Download Energy metabolism patterns in mammalian myocardium adapted to

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ELSEVIER
CardiovascularResearch3 1( 1996)163- 171
Energy metabolism patterns in mammalian myocardium adapted
to chronic physiopathological conditions
Andr6 Rossi, Sylviane Lortet ’
Laboraroire
de Physiologie
Cellulaire
Cardiaque,
Universite’
Joseph Fourier,
BP 53 X-38041,
Grenoble
CEDEX,
France
Accepted22 April 1994
Abstract
Objective: When the myocardium is subjected to a chronic overload, it enlarges and a major restructuring of all organelles and
cellular functions occurs. The changes occurring at the level of the contractile apparatus are well documented; less is known about the
alterations in the energy status of the hypertrophied cardiomyocyte. The purpose of this paper is firstly to provide a brief review of the
data published on this topic and secondly to analyse previously published data drawn from studies devoted to the evaluation of the
capacity of the ATP-producing processes to respond to an acute change in workload. Methods: Several different chronic conditions were
studied in rats: senescence, hypertension, chronic hypoxia, and administration of thyroid hormone. The pattern of the metabolic response
of the heart to acute changes in workload was characterized by alterations in the concentrations of phosphocreatine, inorganic phosphate
and ATF’ followed in isolated heart by 3’P-NMR spectroscopy. Results: In most of the models studied the pattern of these changes was
very similar to that observed in controls. The only exceptions concerned the hearts of young hypertensive rats and those of animals
subjected to a cumulated overload (hypertension + thyroid hormone). Conclusion: Our results demonstrate that the regulation of energy
metabolism was well preserved in spite of the extensive restructuring that occurs in rat hearts subjected to different chronic conditions
which could affect the energy balance of the cardiomyocyte.
Keywords:
Energy metabolism;Heart; Overload;Hypertrophy; Phosphorylatedcompounds
1. Introduction
Under normal work loads and physiological conditions
the heart is capable of matching its rate of energy conversion, through the production of ATP, with the rate of
energy utilization by work. Under physiological conditions
most of the ATP is produced via oxidative phosphorylation
in the mitochondria and the energy conversion process is
closely regulated by the work output of ATP utilization of
the heart (Fig. 1). The mechanisms by which this precise
short-term regulation of mitochondrial respiration occurs
are still unclear and are an area of active research. Several
’ The experimentalresults cited in the paper have been obtainedin
collaborationwith: J. Aussedat, S. Grably, N. Lavanchy, V. Novel, A.
Ray, Laboratoirede PhysiologieCellulaifeCardiaque,Grenoble,France;
H.-G. Zimmer, M. Heckmann, Departmentof Physiology of the University of Munich, Germany; J. Sassard,M. Vincent, Laboratoired’Etudes
Exp&imentales de I’Hypertension, Lyon, France; C. Caldarera, C.
Guamieri,C. Finelli, Departimentodi Biochimica,Universiti di Bologna,
Bologna,Italy.
OOOS-6363/96/$15.000 1996Elsevier ScienceB.V. All rights reserved
SSDI OOOS-6363(95)00183-Z
levels of control have been proposed: availability of ADP
and Pi, adenylate translocation, redox state of the respiratory chain, role of the creatine-kinase shuttle, free cystosolit Ca*+, etc. [see Refs. l-141. As a result of the precise
adjustment of mitochondrial ATP production to the exact
amount of ATP required by external mechanical work and
associated ionic movements, the “macroscopic”
concentration of ATP in the myocardium is, under physiological
conditions, maintained constant even in the course of large
and fast changes in the mechanical activity of the heart.
The short-term changes in the concentrations of the other
phosphorylated compounds (phosphocreatine = PC, inorganic phosphate = Pi, and ADP) in vivo is still a matter of
debate [15], whereas it is now well established that, in
experimental models using isolated hearts, various conditions such as the nature of substrates influence notably the
concentrations of PC and Pi as well as their changes during
work load alterations [ 16- 191.
In several pathophysiological conditions such as chronic
hypertension, constriction of the aorta, valvular insuffi-
164
A. Rossi, S. Lmret/Curdiouamdur
Research
The question may then be raised as to whether, or to
what extent, the hypertrophied myocyte is able to face for
a long time a sustained energy demand and how it responds to fast short-term changes in work load. Indeed, in
most cases cardiac hypertrophy leads to heart failure, the
primary cause of which is still unknown. Moreover, in
several experimental models the initial stage of developing
cardiac hypertrophy is associated with a prolonged decrease in ATP concentration in myocardial tissue [27-301.
This change has even been proposed as a trigger for the
cellular mechanisms leading the hypertrophy [29]. Thus,
the energy function of the myocyte is primarily concerned
with the process of hypertrophy. The nature and mechanisms of the numerous changes that occur are very complex and are not fully understood. A knowledge of them is
of crucial interest both from a fundamental point of view
and for clinical purposes. During hypertrophic growth
fundamental changes take place in excitation-contraction
coupling, in the proportion of connective tissue, and in the
mean diffusion distance from capillaries to intracellular
sites. A review of these alterations is not within the scope
of this paper; however, it is necessary to bear in mind that
such changes may also have crucial consequences on the
energy status of the myocardium.
ciency, arterio-venous fistula, thyrotoxicosis, pheochromocytosis etc., the myocardium is subjected to a chronic work
overload. After the early neonatal period myocardial cells
show a limited capacity for hyperplasia and the heart’s
response to a sustained increase in workload is hypertrophy. This process includes myocardial cell enlargement
and, under some conditions, connective tissue hyperplasia.
However, the hypertrophied tissue is not an identical replica
of the initial tissue. As the heart muscle enlarges, it
undergoes morphological and physiological restructuring
that involves all of the organelles and cellular functions. In
addition, the redesign of myocyte properties and function
also depends on the nature of the stress as well as on the
age and species of the animal involved [20-231.
During aging a moderate cardiac hypertrophy also develops [24,25]. Although the mechanisms and consequences of this process are probably different from cardiac
hypertrophy in young animals, aging is associated with
alterations in electrical activity that are very similar to
those occurring in hypertrophy due to mechanical overload. Since aging is also accompanied by alterations at the
mitochondrial level, it is of interest to compare the energy
alterations associated with this state to those described in
hywqhy
[261.
FFA
31 (19961 163-171
GLUCOSE
Glyeolysis
ATP
A
CK
I
PYRWATE
-PC
-c
Fig. 1. The energy balance in the cardiomyocyte. This figure describes schematically the main components of the energy balance in a myocardial cell. The
main ATP-producing mechanism is oxidative phosphorylation in mitochondria. The process is fed by the production of reducing equivalents (i.e., NADH)
mainly through the tricarboxylic acid cycle (TCA). The substrates are free fatty acids (FFA) and carbohydrates (glucose, lactate, pyruvate). The combined
functions of the respiratory chain (Resp. ch.) with the intervention of oxygen and ATPase (ATP syndtase) allow the rephosphorylation of ADP to ATP.
Adenine nucleotide translocase (ANT) controls the exchange of ATP and ADP between the mitochondrial matrix and cytosol. Several creatine kinases
(CK) participate in’the transfer of energy between ATP and phosphocreatine (PC). The presence of CK specifically bound to mitochondria (CK mito) and
to myofibrils (CK myo) creates an oriented shuttle of energy from mitochondria to myoftbrils. Other CKs are located elsewhere (e.g., in the cytosoi). The
main site of ATP dephosphorylation is myofibrillar ATPase, but other ATPases at several membrane levels (Na+/K+-ATPase, Ca*+-ATPase etc.) also
participate in the splitting of ATP. Several intracellular compounds can play a role in the adjustment of mitochondrial ATP production: phosphorylated
compounds (ADP), redox state (NADH) or calcium (Ca’+ ). The production of ATP is also dependent on oxygen and substrate supply.
A. Rossi, S. Lortet / Cardiovascular
A limited number of studies have been devoted to the
understanding of the energy metabolism status of the
hypertrophied heart. Some data are available on the alterations of the metabolic pathways, on the properties of
mitochondria, or on the enzymatic systems supporting the
transfer of energy in hypertrophied myocardium. The present paper aims to review the main experimental data
dealing with the understanding of the alterations in the
energy status of the cardiomyocyte subjected to hypertrophy. In addition, results drawn from studies in the laboratory dealing with the response of hypertrophied rat hearts
to jumps in workload as observed by 3’P-NMR spectroscopy in isolated hearts will be presented [31-361.
2. Data on the energy metabolism
trophied rat heart
2.1. Consequences of alterations
status of the hyper-
in mechanical properties
Changes in the synthesis of contractile proteins result in
significant alterations in muscle mechanics [37,38] and
energetics [39] because they are associated with marked
changes in myofibrillar adenosine triphosphatase (ATPase)
activity. Moreover, the contraction pattern is also subjected
to large alterations due to reduced activity of the calcium
pumps and to prolongation of the action potential.
A markedly depressed maximum velocity of shortening
has been described in pressure-overloaded rat hearts
[40,41]; in contrast, in response to thyroid hormone intoxication, heart hypertrophy is associated with an increase in
the velocity of shortening of cardiac fibers [41,42]. These
alterations represent the functional consequences of the
isoenzymic redistribution of the V, and V, isoforms of
myosine [43-451. Indeed, the rate of force development
and the velocity of shortening are correlated with the
myocardial V,/V, isoenzyme ratio and with the level of
myosin ATPase activity [39,46-481 whereas the economy
of isometric force development development is inversely
related to this ratio [49]. In the rat myocardium hypertrophied due to the effect of volume overload and thyrotoxicosis there is an increase in V, isoenzyme concentration
whereas in pressure-overloaded rat myocardium the synthesis of myosin is oriented towards the production of the
V, form [48,50,51]. In addition, the nature and extent of
the changes in isoenzymic activities are also sensitive to
species, age, hormonal status and characteristics of the
stress applied to the heart [41,43,44]. Mercadier et al. [44]
reported a shift of the myosin isoenzyme pattern towards
V, as a function of age. In the myocardium of spontaneously hypertensive rats the blood pressure increase during aging is also paralleled by an increase in the V,
myosin isoform [52], the V, form being still predominant
in 12-week-old rats while the V, isoenzyme was the major
form in 18-week-old rats.
The alterations in isoenzyme distribution have important consequences for the bioenergetics of contraction. The
Research
31 (19961163-I
71
165
decrease in myosin ATPase activity and V,/V, ratio observed in pressure-overloaded rat hearts leads to a decrease
in the cross-bridge cycling rate. This adaptation produces a
heart that contracts and develops pressure more economically [41], but its performance may be limited if the rate of
contraction is high. Conversely, in thyrotoxic hypertrophy,
the cross-bridge cycling rate is increased; this results in an
adaptation for pumping large volumes, but the process of
pressure development is far less economical [41].
It is of interest to note that alterations at the level of
other ATPases might also result in significant changes in
mechanical activity. For instance, recent studies performed
by Nagai et al. [53] demonstrated that in heart muscle,
which normally expresses only a slow-twitch sarcoplasmic
reticulum ATPase, modulation of the synthesis of this
isoenzyme occurs in hypertrophy. In response to pressure
overload the level of this system decreases by 34% whereas
it is raised to 67% above control level after only 3 days of
thyroid hormone treatment.
2.2. Energy metabolism
During the early stages of a cardiac overload the synthesis of mitochondria is enhanced [54] and these organelles increase in number [55,56]. Several papers report,
in compensated hypertrophy, a normal or decreased mitochondrial volume which parallels the increased myofibrillar components [55-571, but the number of mitochondria
per unit cross-sectional area is increased [58,59]. It remains
to be understood whether a larger number of smaller
mitochondria is adequate for the larger than normal contractile mass in the hypertrophied cardiomyocyte. Conceming the function of mitochondria, most earlier studies
found normal oxidative metabolism in compensated heart
hypertrophy 1601, but other studies describe an increase in
respiratory enzyme activities in response to various stimuli
such as pressure overload [28,61], aortic insufficiency [62],
and thyroid hormone administration [60]. Respiratory control (ADP/O ratio and H+/O) seems not to be affected by
cardiac hypertrophy [63-661 or by age [67,68].
Several recent observations suggest that some defects in
the ATPase activity of mitochondria could arise in hypertrophied cardiomyocytes [69-711.
Mitochondrial proteins are encoded by both nuclear and
mitochondrial genes; consequently, mitochondrial biogenesis must involve the coordinated expression of both
genomes. This is particularly crucial for the synthesis of
the mitochondrial FoF, ATP synthase complex. The F,
catalytic sector is composed of 5 nuclear encoded subunits
while the F, membrane sector is made up of 7 polypeptides: 2 encoded by the mitochondrial genome and the
others by the nuclear genome [72]. A decrease in ATPase
activity, accompanied by an increase in oligomycin-sensitive proton conduction of the rat heart, has been detected
in senescent animals (24 months) [71]. This has been
attributed to a larger decrease in F, content than that
166
A. Rossi, S. Lortet/Curdiovoscuiur
Research
31 11996) 163-171
of PC production and energy supply to the myofibrils since
these isoenzymes are located in the cytoplasm and do not
participate in the highly effective coupled reactions at the
level of the mitochondria, myofibrils or sarcolemma. Regarding mitochondrial creatine kinase, which is supposed
to have tight functional coupling with adenine nucleotide
translocase [80], a deficiency has been detected in several
cardiomyopathies 188-90-J.
observed for F,, [71], which leads to a dissipation of the
electrochemical proton gradient. Defects in the regulation
of mitochondrial ATP synthase have also been detected in
cardiomyocytes from spontaneously hypertensive rats [69]
and in cardiomyocytes from thyroxine-treated rats [70]. In
both situations the basal ATP synthase capacity was raised
in quiescent cells compared to control animals, but ATP
synthase activity was not increased in response to an acute
rise in energy demand. The authors concluded that the
regulation of mitochondrial ATP synthase was defective
due to a possible increase in intramitochondrial calcium
content [69,70]. An uncoordinated transcription of the respiratory chain components encoded at the nuclear level has
also been reported in thyrotoxicosis [73]. In aged rat
myocardium alterations of the function of the mitochondria
are to be expected since superoxide generation has been
reported [74].
In several models of cardiac hypertrophy an increased
glycolytic enzyme level and a shift in lactate dehydrogenase isoenzyme towards the skeletal muscle pattern has
been shown [75-771. These isoenzyme shifts, particularly
that of phosphofructokinase, a key enzyme of glycolysis
(77), result in a more anaerobic-type pattern [75]. In
parallel a decrease in the rate of fatty-acid metabolism has
been detected in hypertrophied hearts in association with a
possible fall in camitine availability [78]. It is of interest to
note that there is also an increase in glycolytic rates in the
hearts of aged rats [24,79].
The creatine phosphate-creatine kinase system, which
plays a major role in the transfer of energy in the myocyte
[80-831, is also profoundly altered in hypertrophied hearts.
In hypertrophied cardiomyocytes the production of cytosolit forms MB and BB of creatine kinase is increased
[84-871. Such a shift in creatine kinase isoenzyme from
MM forms (found in the adult rat heart and functionally
coupled with myofibrillar ATPase) to MB and BB forms
(characteristic of developing muscle) may lower efficiency
3. Response of myocardial energy metabolism to acute
increases in work: studies, by 31P-NMR, on hearts
isolated from rats subjected to chronic pathophysiological conditions
Non-invasive monitoring, by means of 3’P-NMR spectroscopy, of the intramyocardial ATP, phosphocreatine
(PC) and inorganic phosphate (Pi) contents of isolated rat
heart has been used to follow the time-course of alterations
provoked by acute changes in heart work. Such a technique has been applied to hearts from rats subjected to
various chronic cardiac overload. This paper gives a brief
comparative review of published and unpublished results.
3.1. Principle (Fig. 2)
When the level of mechanical work developed by the
myocardium is increased, the amount of ATP synthetized
is adjusted to match exactly the demand. Schematically 3
mechanisms participate in the phosphoxylation of ADP: the
main one is oxidative phosphorylation at the mitochondrial
level, secondly a limited amount of ATP can be produced
anaerobically during glycolysis, and thirdly any decrease
in ATP content is immediately matched by PC degradation
under the action of creatine-kinase (CK). Under physiological conditions ATP is mainly produced by the first
mechanism provided that oxygen and substrate delivery is
GLUCOSE
W
Lactate
J
Cr
Fig. 2. Energetics of cardiac muscle contraction. Part of the free energy of ATP hydrolysis is used to develop mechanical work (W); this reaction produced
ADP and inorganic phosphate (Pi). The resynthesis of ATP is supported by 3 mechanisms: (1) the mitochondrial phosphorylation of ADP under the effect
of ATPase (ATP synthase) - the substrates are free fatty acids @PA) and glucose (or derivatives); (2) the anaerobic degradation of glucose to lactate; (3)
the coupled degradation of phosphocreatine (PC) to creatine (Cr> through the creatine kinase (CK) reaction. Mechanism (3) can be switched on
immediately upon changes in the concentrations of reactants (Pi and ADP mainly). To increase the rates of ATP production through processes ( 1) and (3)
requires adjustment of enzymatic activities and an adequate supply of substrates and oxygen.
A. Rossi, S. Lortet /Curdiouascular
Research
31 (1996)
163-I
167
71
by the left ventricule (LVDP) was measured by means of
an intraventricular balloon. The hearts were paced at 6 Hz
and inserted in a sealed cylindrical glass chamber which
was placed into the NMR detection coil. 3’P-NMR measurements were performed at 81 MHz, NMR spectra (2.5
min) were collected, and the areas under the resonance
peaks of PC, Pi and BP-ATP were used to calculate the
respective intramyocardial contents. The data were expressed as cytosolic concentrations assuming a cytosolic
space of 600 ~1. g- ’ wet weight and taking the ATP
content biochemically determined as an internal standard.
The perfusion medium contained: NaCl 118 mM, KC1
5.6 mM, MgCl, 2.4 mM, NaHCO, 21 mM, glucose 9
mM, pyruvate 2 mM and variable amounts of CaCl,
(0.5, 1, 1.5, 2 mM). It was gassed with a 95% O,-5%
CO, mixture. The pH was kept at 7.4 and the temperature
at 37°C. Stepwise changes in work, monitored by LVDP,
were elicited by changing the concentration of calcium in
the perfusion fluid.
The physiopathological conditions studied were: aging,
22-24-month-old
Wistar rats [36]; spontaneously hypertensive rats (SHR) from the Lyon strain studied at two
ages-3 and 6 months [33-351; SHR [34]; Sprague-Daw-
adequate. When pyruvate is provided in the perfusion
medium of isolated hearts, one can assume that the substrate supply is not limiting as would be the case with
glucose alone. Moreover, with a sufficiently high concentration of pyruvate, pyruvate dehydrogenase is maximally
activated, leading to an increase in the mitochondrial
NADH level. Thus, the regulation of oxidative phosphorylation is expected to shift from intramitochondrial
redox
potential to phosphorylated compounds: ADP, Pi or derived index [17,30]. As a consequence it can be predicted
that, under acute increasing work load, extensive alterations in Pi, PC and ADP occur. In addition, we can
assume that ATP production from glucose is negligible
since glycolysis is probably inhibited due to the effect of
pyruvate. Lastly, in these experiments the level of work
developed by the hearts can be kept relatively low so that
the oxygen supply is not limiting in such a perfusion
model.
3.2. Methods
The methods have been described in detail in previous
papers [32-3.51. In brief, rat hearts were perfused via a
cannula inserted into the aorta and the pressure developed
Table 1
Phosphorylated compound contents and metabolic response to increase in work in hearts isolated from rats under several pathophysiological conditions
Metabolite concentration (mM)
Metabolic
References
at low work
response to
(LVDP 30 mmHg)
work jump
(to LVDP 50 mmHg)
ATP
Controls
(Adult: 6- 12 months)
Young Wistar
3 months
Aged Wistar
22-24 months
7-8
PC
12-13
=
=
L
Chronic hypoxia
Hypertension
LH strain
3 months
LH strain
Adult: 6 months
Adult Wistar
Pi
<I
AP,
=
0.8- 1.5
mM
=
32-37
36
=
=
=
36
=
J#
=
=
(‘)
nd
i
t
T
nd
=
=
=
33-35
=
=
=
T
34
=
1
L
J
=
t
=
=
33
34
33-35
Hyperthyroidism
T3-treated:
Adult Sprague-Dawley
Adult Wistar SHR
The data are drawn from the publications cited in the references. The conditions were as follows: SHR = spontaneously hvoertensive
rats. Lvon Strain and
..
Wistar strain; T, = daily treatment with triiodotyronine (0.2 mg. kg- ’ s.c.) for 14 days. Chronic hypoxia = 3 weeks at 10% oxygen, normobaric. The table
gives the significant changes relative to the values in hearts from the respective control groups: = not significantly different, t significantly increased, 1
significantly decreased, nd = not determined. The values given for the controls indicate the range of variation in the different control groups. The
concentrations of metabolites were determined on hearts perfused with 0.5 mM Ca*’ developing a low ventricular pressure ( < 30 mmHg). The metabolic
response to a work jump (to 50 mmHg left ventricular pressure) elicited by increasing the concentration of calcium in the perfusion fluid is expressed as
the increase in the concentration of inorganic phosphate (Pi).
* Unpublished results.
A. Rossi. S. Lortet /Curdiovascular
168
calcium (mM)
2
1.5
F
15
10
t
ATP (mM)
Fig. 3. Changes in function and in phosphorylated
compound concentrations of isolated hearts, elicited by stepwise elevation of the calcium
concentration
in the perfusion fluid. Isolated rat hearts were perfused via
the aorta with a medium containing glucose 9 mM and pyruvate 2 mM.
The concentration
of calcium was 0.5 mM for the first 30 mm of
perfusion time; it was then switched to 1, 1.5 and 2 mM for successive
periods of 10 min each followed by 10 mm perfusion with 0.5 mM Ca*+.
Left ventricular
developed pressure (LVDP)
was measured by means of
an intraventticular
balloon connected to a pressure transducer. The intramyocardial
concentrations
of phosphocreatine
(PC), ATP, and inorganic phosphate (Pi) were calculated from 3’P NMR spectroscopy
data
collected over 2 min spectra.
ley [33] and SHR rats (34) treated for 14 days with
subcutaneous injections of triiodothyronine CT,, 0.2 mg .
kg-’ S.C. daily) and chronic hypoxia for 3 weeks at 10%
oxygen normobaric [unpublished results].
3.3. Results and discussion
The protocol used in these experiments permitted gradual and reversible changes in LVDP as shown in Fig. 3.
These changes in developed work load were associated
with graded: and reversible alterations in PC and Pi contents. Moreover, following an increase or decrease in the
level of heart work, steady states characterized by constant
PC and Pi concentrations were reached. We used the PC
and (or) Pi concentrations at steady-state levels to characterize the metabolic state of the hearts for a given work
level.
Research
31 (19%)
163-171
In order to evaluate the energy status of the heart
following a period of imposed chronic overload or hypoxia
(Table 11, we measured the concentration of ATP in
freeze-clamped hearts. PC and Pi concentrations were calculated from NMR spectra taken at the beginning of
perfusion when the heart developed a low work level
(LVDP at about 30 mmHg at 0.5 mM calcium). A significant decrease in ATP content was observed in the hearts of
senescent rats. This alteration, which was not accompanied
by changes in PC and Pi levels, probably reflects the
well-documented increase in connective tissue relative to
cardiomyocytes. The administration of triiodothyronine to
spontaneously hypertensive rats induced all the alterations
characteristic of a failure in energy production: PC and
ATP degradation and Pi accumulation. In all other situations, including chronic hypoxia, ATP concentration was
not altered, indicating that the overload imposed on the
heart in situ was progressive enough to allow the development of adaptive processes. This is not the case in other
experimental models of cardiac overload such as aortic
stenosis in adult animals or repeated administrations of
isoprenaline in which a degradation of ATP has been
observed [30]. The decrease in PC content when associated
with an accumulation of Pi, as observed in young hypertensive rats submitted to T, treatment, probably reflects an
energy imbalance. On the other hand, the decrease in PC
content detected in TX-treated animals can be interpreted to
be a consequence of disturbances in the metabolism of
creatine rather than a result of energy imbalance. This is
probably also the case for hypoxic animals.
The alterations in ATP, PC and Pi concentrations when
the isolated hearts were subjected to jumps in work, elicited
by increasing the calcium content of the perfusion fluid,
can be summarized as follows. In none of the conditions
studied did we detect any alteration in ATP concentration.
Since PC content was decreased in several groups of hearts
prior to the jump in work, a comparison between groups
has been made using the increases in Pi concentrations in
response to the increase in LVDP. The choice of AP, as an
index of the reactivity of energy metabolism was also
governed by the following reasons: (1) the signal detected
by NMR gives a good image of the true cytosolic concentration of Pi; (2) this metabolite is directly and immediately
affected by any increase in cytoplasmic ATP utilization
(Fig. 2); and (3) the Pi concentration in the range 0.5-2
mM probably plays, as substrate, a regulating role for
mitochondrial ATPase [l]. The data collected in Table 1
demonstrate that surprisingly, under most of the conditions
studied, the metabolic responses of the hearts were very
similar to those seen in control hearts. This demonstrates
that the intrinsic properties of the ATP-producing processes of the cardiomyocyte are not altered in these hearts,
at least for moderate levels of work load. Interestingly, in
young hypertensive animals, the stepwise increase in work
load was accompanied by a larger accumulation of Pi than
in controls, but this phenomenon was abolished as the rats
A. Rossi. S. Lortet / Cordiouasculur
grew older. In the Wistar SHR, which were subjected to a
higher in vivo blood pressure, the greater accumulation of
Pi than in controls was still present during adulthood. This
discrepancy in metabolic response compared to controls
disappeared under the effect of T, treatment. This result
demonstrates that, even if the energy profile of these hearts
was profoundly altered, the metabolic response to a jump
in work was preserved. Therefore, it can be concluded that
a possible adaptation in energy metabolism might develop
during cardiac growth and T, treatment.
Resawch
Dl
31 (1996)
production
[2]
Chance
rylation.
Nishiki
potenJ Mol
to oxidative
phosphorylation.
J Biol
Chem.
1980;255:
755-763
[51 Erecinska
M, Wilson
J. Membrane
161Jacobus WE,
tory
Annu
181Gibbs
DF. Regulation
of cellular
Biol 1982;70:
1- 14.
Moreadith
RW, Vandegaer
control:
evidence
against
the
KM.
potentials
and
by
energy
metabolism.
Mitochondrial
regulation
phosphorylation
1982;257:2397-2402.
WE. Respiratory
control
phosphate
metabolism
respira-
of respiration
by ex-
or by ATP/ADP
the integration
mitochondrial
Rev Physiol
1985;47:705-725.
C. The cytoplasmic
phosphorylation
ratios.
of heart highcreatine
kinase.
potential.
Its possible
role in the control
of myocardial
respiration
and cardiac
contractility.
J Mol Cell Cardiol
1985; 17:727-73
I.
IE. Mitochondrial
respiratory
control
in the myocardium.
[91 Hassinen
Biochim
Biophys
Acta 1986;853:
135- 15 I.
of oxidative
phosphorylation
in the mam[lOI Balaban RS. Regulation
[III
malian
Denton
cell. Am J Physiol
Rm, McCormack
mitochondria
[I21
of
the
1990;258:C377-C389.
JG. Ca2+
as a second
heart
1990;52:451-466.
Heinemann
FW, Balaban
the heart in viva. Annu
and
T, Wyss
M, Brdiczka
Intracellular
compartmentation,
kinase
isoenzymes
in tissues
[I41
work
and
RS, Kantor
phosphate
of some
epinephrine
isolated,
Annu
within
Rev
of mitochondrial
1990;52:523-542.
Physiol
respiration
in
D, Nicolay
K, Eppenberger
HM.
structure
and function
of creatine
with
high
and fluctuating
energy
HL, Katz
metabolite
heart. Science
1986;232:
Matthews
PM, Williams
messenger
tissues.
demands:
the phosphocreatine
circuit
for
statis. Biochem
J 1992;281:21-40.
Harris
DA, Das AM. Control
of mitochondrial
heart. Biochem
J 1991;280:561-573.
1151 Balaban
[I61
other
RS. Control
Rev Physiol
iI31 Walliman
cellular
ATP
LA, Briggs
RW.
in the in vivo
I 12l- I 123.
SR, Seymour
AM,
energy
homeo-
synthesis
in the
Relation
between
paced
mammalian
et al. A “P-NMR
study
metabolic
and functional
effects
of the inotropic
agents
and ouabain,
and ionophore
R02-2985
(X537A)
on the
perfused
rat heart.
Biochim
Biophys
Acta
1982;720:163-
171.
[I71 From
AHL,
“P-NMR
cardium.
1181Katz
LA,
glucose
Petein
studies
MA,
Michurski
on respiratory
SP, Zimmer
regulation
on
FEBS Lett 1986;206:257-261.
Koretzky
AP, Balaban
perfused
heart. A 3’ P NMR
Lett 1987;221:270-276.
LA, Koretzky
AP, Balaban
activity
and cardiac
respiration:
SD, Ugurbil
K.
the intact
myo-
RS. Respiratory
control
and NADH
fluorescence
in the
study.
FEBS
1191 Katz
1988;255:Hl85-H188.
M, Zak
DO1 Rabinowitz
in
185.
RS. Activation
of dehydrogenase
a 3’P-NMR
study.
Am J Physiol
R. Biochemical
hypertrophy.
Annu Rev
1211Zak R. Factors controlling
the Heart
1984; 165-
[I]
of phosphorylation
perfused
rat hearts.
CA, Kupriyanov
VV, Elizarova
GV, Jacobus
WE. Studies
of
energy
transport
in heart cells.
The importance
of creatine
kinase
localization
for the coupling
of mitochondrial
phosphorylcreatine
energy
References
169
[41 Saks
[71 Jacobus
It is well established that, in response to a variety of
stresses, fundamental changes occur in the structural and
functional characteristics of the cardiomyocyte. Moreover,
a full understanding of cardiomyocyte function must also
take into consideration the well-known age-related changes,
especially during the transition from adulthood to senescence.
These changes involve a coordinated re-organization of
contractile excitation-contraction
coupling. The thermodynamic consequences of alterations in the nature of the
contractile proteins are particularly well documented from
experiments on the rat heart. In other species, including
human, the changes in contractility have still to be completely elucidated from the knowledge of changes occurring at other levels (sarcolemma, sarcoplasmic reticulum).
The alterations produced by different stress situations
on the ATP-producing systems and mainly on mitochondria are much less well known. Several experimental observations have led to the conclusion that mitochondrial
defects arise in hypertrophy and senescence, but the evidence remains equivocal. Our experiments studied the
capacity of the energy process of the rat heart to respond
to acute increases in work load. It appeared that, in several
experimental models of cardiac hypertrophy, the global
metabolic behaviour of the heart submitted to acute jumps
in work load was very similar to that of control hearts
despite changes occurring in the concentrations of ATP or
PC at low work load. Only in the case of young hypertensive animals did we detect signs of disturbances in the
metabolic response of the heart. It seems, therefore, that in
most situations the various changes that occur at the level
of the different organelles do not result in a loss of
regulation of energy balance and ATP turnover.
71
Giesen
J, Kammermeier
H. Relationship
tial and oxygen
consumption
in isolated
Cell Cardiol
1980; I2:89 l-907.
tramitochondrial
J Biol Chem
4. Conclusions
163-I
Health
and
cellular
Med 1972;23:245-262.
cardiac
growth.
and
Disease.
New
changes
In: Zak
York:
in cardiac
R, cd. Growth
Raven
of
Press,
ml
B, Williams
G. Respiratory
enzymes
J Biol Chem
1955;217:383-393
K, Erecinska
M, Wilson
DF. Energy
cytosolic
perfused
234:C73-C8
metabolism
rat heart
I.
and mitochondrial
under
various
work
in oxidative
relationships
respiration
loads.
Am
in the
.I Physiol
phospho-
Swynghedauw
B. Developmental
and functional
adaptation
of contractile
proteins
in cardiac
and skeletal
muscle.
Physiol
Rev
1986;66:710-771.
L, Zak R. Biological
mechanism
of hypertrophy.
In:
[231 Bugaisky
between
isolated
1978;
D4l
Fozzard
HA et al., ed.: The Heart and Cardiovascular
York: Raven
Press, 1986; I49 I - 1506.
Lakatta
EC. Yin FCP. Myocardial
ageing:
functional
related
cellular
mechanisms.
Am J Physiol
System.
New
alterations
and
1982;242:H927-H94l.
170
A. Rossi, S. Lortct / Cardiovusculur
[25] LaJcatta EG. Cardiac muscle changes in senescence. Annu Rev
Physiol 1987;49:5 19-53 1.
[26] Hansford
RG. Bioenergetics
in ageing. Biochem
Biophys
Acta
1983;726:41-80.
[27] Pool PE, Spann JE, Buccino RA, Somtenblick
EH, Braunwald
E.
Myocardial
high energy phosphate stores in cardiac hypertrophy
and
heart failure. Circ Res 1967;21:365-372.
[28] Meerson FZ. The myocardium
in hyperfunction,
hypertrophy,
and
heart failure. Circ Res 1969;2%suppl
II): 1- 163.
[29] Meerson FZ, Pomoinitsky
VD. The role of high-energy
phosphate
compounds in the development
of cardiac hypertrophy.
J. Mol Cell
Cardiol I972;4:57 l-597.
[30] Zimmer
HG, Gerlach
E. Early metabolic
alterations
during the
development
of experimentally
induced
cardiac
hypertrophy.
Arzneim-Forsch./Drug
Res 1980;30:2001-2007.
[31] Lortet S, Zimmer
HG, Rossi A lnotropic response of the rat heart
during development
and regression of triiodothyronine-induced
hypertrophy.
J Cardiovasc Pharmacol 1989; 14707-712.
[32] Aussedat J, Ray A, Lortet S, Reutenauer
H, Grably S, Rossi A.
Phosphorylated
compounds
and function in isolated hearts: a “PNMR study. Am J Physiol 1991;260:HllO-HI
17.
[33] Aussedat J, Lortet S, Ray A et al. Energy
metabolism
of the
hypertrophied
heart studied by 3’ P nuclear magnetic resonance.
Cardioscience
1992;3:233-239.
[34] Heckmann
M, Lortet S, Aussedat J, Ray A, Rossi A, Zimmer AG.
Function and energy metabolism
of isolated hearts obtained from
hyperthyroid
spontaneously
hypertensive
rats (SHR). A ” P nuclear
magnetic resonance study. Moll Cell Biochem 1993;119:43-50.
[35] Lortet S, Heckmann
M, Aussedat J, et al. Alteration
of cardiac
energy state during development
of hypertension
in rats of the Lyon
strain: a 3’P-NMR
study on the isolated rat heart. Acta Physiol
Stand 1993;149:311-321.
[36] Finelli C, Aussedat J, Ray A, et al. Effect of age on phosphorylated
compounds
and mechanical
activity of isolated rat hearts: a 3’P
NMR study. Cardiovasc Res 1993;27: 1978-1982.
[37] Alpert NR, Hamrell BB, Halpem W. Mechanical
and biochemical
correlates of cardiac hypertrophy.
Circ Res 1974;34(suppl
II):7 I-82.
[38] Jacob R, Kissling G, Rupp H, Vogt M. Functional
significance
of
contractile proteins in cardiac hypertrophy
and failure. J Cardiovasc
Pharmacol:
1987;lO (suppl 6):S12-S12.
[39] Alpert NR, Mulieri
LA. Heat, mechanics
and myosin
ATPase
activity
in normal
and hypertrophied
heart muscle.
Fed Proc
1982;41:192-198.
[40] Maughan
D, Low E, Litten R, Brayden
J, Alpert N. Calcium
activated muscle from hypertrophied
rabbit hearts. Mechanical
and
correlated biochemical
changes. Circ Res 1979;44:279-287.
[4l] Alpert NR, Mulieri
LA. Determinants
of energy utilization
in the
activated myocardium.
Fed Proc 1986;45:2597-2600.
[42] Hoh JFY, Egerton LJ. Action of triiodothyronine
on the synthesis of
rat ventricular
myosin isoenzymes.
Febs Lett 1979; IO I : l43- 148.
[43] Lompre AM, Schwartz K, Albis A, Lacombe G, Thiem NV, Swynghedauw B. Myosin isozymes redistribution
in chronic heart overloading. Nature (Land.) 1979;282: IOS- 107.
[44] Mercadier
JJ, Lompre AM, Wisnewsky
C, Samuel JL, Bercovici
J,
Swynghedauw
B, Schwartz K. Myosin isoenzyme changes in several
models of rat cardiac hypertrophy.
Circ Res 1981;49:525-532.
1451 Swynghedauw
B, Moalic JM, Lecarpentier
Y. et al. Adaptational
changes in contractile proteins in chronic cardiac overloading:
structure and rate of synthesis. In: Alpert NR, ed. Myocardial
Hypertrophy and Failure. New York: Raven Press, 1983;46-476.
[46] Schwartz K, Lecarpentier
Y, Martin JL, Lompre AM, Mercadier
JJ,
Swynghedauw
B. Myosin
isoenzymic
distribution
correlates with
speed of myocardial
contraction.
J Mol Cell Cardiol 1981; 13: 107l1076.
[47] Pagani ED, Julian FJ. Rabbit papillary muscle isoenzymes
and the
velocity of papillary muscle shortenin,. 0 Circ Res 198454586-594.
[48] Hammll B, Alpert NR. Cellular basis of mechanical
properties of
Research
[49]
[50]
1511
1521
[53]
[54]
]55]
1561
[57]
[58]
[59]
[60]
[61]
1621
]63]
1641
]65]
[66]
]67]
(681
]69]
31 (1996)
163-I
71
hypertrophied
myocardium.
In: Fozzard
HA et al., eds. The Heart
and Cardiovascular
system. New York: Raven Press, 1986, 15071524.
Alpert NR, Mulieri
LA Thermomechanical
economy of hypertrophied hearts. In: Alpert, NR, ed. Myocardial
Hypertrophy
and
Failure. New York: Raven Press, 1983; 619-630.
Litten RZ, Martin BJ, Low RB, Alpert NR. Altered myosin isoenzyme patterns from pressure-overloaded
and thyrotoxic
hypertrophied rabbit hearts. Circ Res 1982;50:856-864.
Schiaffino
S, Gorza L, Sartore S. Distribution
of myosin types in
normal and hypertrophied
hearts: an immunocytochemical
approach.
In: Alpert, NR, ed. Myocardial
Hypertrophy
and Failure. New York:
Raven Press, 1983; I49- 166.
Morano I, Lengsfeld M, Ganten U, Ganten D, Ruegg JC. Chronic
hypertension
changes myosin
isoenzyme
pattern and decreases
myosin phosphorylation
in the rat heart. J Mol Cell Cardiol 1988;
20:875-886.
Nagai R, Zarin-Herzberg
A, Brand1 CJ, et al. Regulation of myocardial Ca*+ ATPase and phospholamban
mRNA expression
in response to pressure overload and thyroid hormone. Proc Nat1 Acad
Sci USA 1989;86:2966-2970.
Zak R, Rabinowitz
M. Molecular
aspects of cardiac hypertrophy.
Annu Rev. Physiol 1979;41:539-552.
Page E, Polimeni PI, Zak R, Earley J, Johnson M. Myofibrillar
mass
in rat and rabbit heart muscle: correlation
of microchemical
and
stereological
measurements
in normal and hypertrophied
heart. Circ
Res 1972;30:430-439.
Zak R, Rabinowitz
M, Rajamanickam
C, Merten S, KwiatkowskaPatzer B. Mitochondrial
proliferation
in cardiac hypertrophy.
Basic
Res Cardiol 1980;75:171-178.
Anversa P, Loud AV, Vitali-Mazza
L. Morphometry
and autoradiography of early hypertrophic
changes in the ventricular
myocardium
of adult rat: an electronic
microscopic
study.
Lab Invest
1976;35:475-483.
Bishop SP, Cole CR. Ultrastructural
changes in the canine myocardium with right ventricular
hypertrophy
and congestive
heart
failure. Lab Invest 1969;20:219-229.
Hatt PY. Cellular changes in mechanically
overloaded
heart. Basic
Res Cardiol 1977; 72: 198-202.
Rabinowitz
M, Zak R. Mitochondria
and cardiac hypertrophy.
Circ
Res 1975;36:367-376.
Albin R, Dowel1 RT, Zak R, Rabinowitz
M. Synthesis and degradation of mitochondrial
components
in hypertrophied
rat heart.
Biochem J 1973; 136:629-637.
Fizelova A, Fizel A. Cardiac hypertrophy
and heart failure: dynamics of change in proteins and nucleic acids. J Mol Cell Cardiol
1970; 1:389-402.
Stoner CO, Ressalat MM, Strak HD. Oxidative
phosphorylation
in
mitochondria
isolated from chronically
stressed dog hearts. Circ Res
1968;23:87-97.
Cooper G, Satava RM, Harrison CE, Coleman HN. Mechanisms for
abnormal
energetics
of pressure-induced
hypertrophy
of the cat
myocardium.
Circ Res 1973;33:213-223.
Sordahl LA, McCollum
WB, Wood WG, Schwartz A. Mitochondria
and sarcoplasmic
reticulum
function
in cardiac hypertrophy
and
failure. Am J Physiol 1973;224:497-502.
Rouslin W, Cubicciotti
RS, Edwards WD, et al. Phosphorylative
respiratory
activity
of mitochondria
isolated from left and right
ventricles of rabbit hearts following
partial pulmonary
trunk occlusion. J Mol Cell Cardiol 1979; I I :91-99.
Manzelmann
MS, Harmon HJ. Lack of age dependent changes in rat
heart mitochondria.
Mech Ageing Dev 1987;39:28 l-288.
Gadaleta MN, Petruzzella
V, Renis M, Fracasso F, Cantatore D.
Reduced transcription
of mitochondrial
DNA in the senescent rat.
Tissue dependence and effect of acetyl-L-camitine.
Eur J Biochem
1990;187:501-506.
Das AM, Harris DA. Defects in regulation
of mitochondrial
ATP
A. Rossi.
synthase
in cardiomyocytes
Am J Physiol
1990;28:Hl264-Hl269.
AM,
Harris
[70]
Das
[71]
cardiomyocytes:
effects
of thyroid
1991;1096:284-290.
Guerrieri
F, Capozza
G, Kalous
Age-dependent
[72]
of F,Fa
by thyroid
BD.
hormone
rat hearts.
ed.
Cardiac
Biochim
M, Zanotti
bovine
Biophys
S.
[81]
mitochondria.
levels
Biochem-
for nuclear-encoded
components
are regufashion.
New
Press,
[77]
JRE, Singhal
RL, Parulekar
MR. Beznak
M. Influence
glucose-6-phosphate
dehydrogeaortic
coarctation
on myocardial
nase. Can J Physiol
Pharmacol
1969;47:388-391.
Seymour
AML,
Eldar
H, Radda
GK. Hyperthyroidism
results
[78]
increased
glycolytic
capacity
Biochim
Biophys
Acta 1990;
El Alaoui-Talibi
Z, Moravec
[79]
palmitate
Biochim
Abu-Erreish
rat
V, Sanadi
WE,
Saks
in its kinetic
Smimov
Science
VN,
function
hearts
Chazov
and
of energy
of aged
El.
Role
metabolism.
in muscle.
The
creatine
kinase
isoenzyme.
Ingwall
JS. Kramer
MF,
in normal
and diseased
J
phos-
I98 I ;2 I I :488-492.
VA.
Creatine
properties
shuttle”.
hypertrophied
of
Can
kinase
induced
of
by
heart
coupling
mitochondria:
to oxidative
Arch Biochem
Biophys
I982;2 19: 167- 178.
Sweeney
HL, Kushmerick
MJ. A simple
analysis
[86]
Younes
kinase
A, Schneider
isoenzymes
cardium.
Cardiovasc
[87]
Smith
SH, Kramer
changes
in creatine
of
[88]
in
in the rat heart.
A “P-NMR
study.
1055: lO7- I 16.
J. Camitine
transport
and exogenous
in chronically
volume-overload
Acta 1989;1003:
109-l
14.
Neely
JR, Whitmer
JT, Whitman
shuttle.
[84]
mechaIn: Alpert
Academic
LV,
working
Am J Physiol
myocardium
1984;246:C365-377.
accumulates
the
of the
MB-
Eur Heart J I984;5(suppl
F): I29- 139.
Fifer MA, et al. The creatine
kinase system
human
myocardium.
N Engl
J Med
1985;313:1050-1054,
1990;1015:200-204.
York:
by isolated
perfused
1977;232:E258-E262.
Rosenshtraukh
“phosphocreatine
Ingwall
JS. The
Mitochondrial
particles
glycolytic
failure.
Jacobus
changes
171
phosphokinase
in cellular
Pharmacol
1978;56:691-706.
SP, Geiger
PJ. Transport
phosphorylation.
Meyer
RA,
[85]
Acta
VV,
[83]
Eur J Biochem
C, Caldarera
CM.
from submitochondrial
163-171
phorylcreatine
of the
1971567-585.
Valadates
oxidation
Biophys
GM,
Saks
creatine
Physiol
Bessman
synthase.
Identification
Evidence
for increased
and congestive
heart
Hypertrophy.
[80]
Acta
Z, Papa
ATP
31 (1996)
Fatty acid oxidation
rats. Am J Physiol
[82]
MJ.
heart
in an uncoordinated
in rat
Biophys
FaF,
Rrseurch
rats.
synthase
F, Drahota
mitochondrial
Transcript
respiratory-chain
Biochim
Bishop
SP, Atschuld
RR.
nism in cardiac
hypertrophy
NN,
[76]
from
ATP
hormone.
14:299-308.
A, Runswick
Cordiouuscuhr
hypertensive
of mitochondrial
in the
ATPase
spontaneously
1992;207:247-25
I.
Muscari
C, Frascaro
M, Guamieri
function
and superoxide
generation
of aged
[75]
changes
istry 199 I ;30:5369-5378.
Luciakova
K, Nelson
mammalian
mitochondrial
lated
[74]
Control
Arch Gerontol
Geriatr
1992;
Walker
JE, Lutter
R, Dupuis
subunits
[73]
DA.
from
S. Lortet/
hearts.
DR.
[%I
Res
1985;
J, Swynghedauw
B. Creatine
chronically
overloaded
myo-
19: 15- 19.
MF, Reis I, Bishop
kinase
and myocyte
SP, lngwall
JS. Regional
size in hypertensive
and
nonhypertensive
cardiac
hypertrophy.
Circ Res 1990;67:
1334- 1344.
Veksler
VI, Ventura-Clapier
R, Lechene
P, Vassort
G. Functional
state of myotibrils,
mitochondria
and bound
creatine
kinase
in
skinned
Cardiol
[89]
JM, Bercovici
redistribution
in
ventricular
fibers
1988;20:329-342.
of cardiomyopathic
hamsters.
J Mol
Cell
Savabi
F. Mitochondrial
creatine
phosphokinase
deficiency
in diabetic rat heart. Biochem
Biphys
Res Commun
1988;154:469-475.
Popovitch
BK, Boheler
KR, Dillmann
WH. Diabete
decreases
creatine kinase
enzyme
activity
and mRNA
level in the rat heart. Am J
Physiol
1989;257:E573-E577.