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Sensitivity of the Large Blood Vessels of the Rabbit to
i-Epinephrine and i-Norepinephrine
By
J O H N A. BEVAN, M.B.,
B.S.
With the technical assistance of J. V. Osher, Pli.B., B.A.
T
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jugular vein; the first 2 cm. of the common iliac
and femoral arteries, the lower lobar pulmonary
artery, and the anterior and posterior mesenterie
arteries; the caudal half of the inferior vena cava;
the abdominal aorta distal to the origin of the
renal arteries; and the whole of the celiac artery
and the adjacent part of its gastrohepatic branch.
The width of the strips prepared from the largest
arteries and from the veins was approximately
0.5 em.; from the medium-sized vessels, such
ns the renal artery, 0.3 to 0.4 cm.; and from the
smaller vessels, such as the saphena artery, 0.25
to 0.15 em.
With available apparatus, it was possible to
examine four preparations at a time. The thoracic
aorta, which was used throughout as a standard,
and three other vessels were removed from each
animal and mounted in four separate baths. They
were attached by ligatures to isotonic levers
that wrote simultaneously on the same kymograph. These levers were counterbalanced to exert
tensions between 0.5 to 3.0 Gin. on the preparations. A pilot experiment was conducted with a
preparation from each anatomically distinct vessel
to determine the load for optimum contraction.
All preparations were mounted in bicarbonate
buffered Krebs saline solution containing glucose
200 Mg. per cent w/v and disodium versenate
0.2 Mg. per cent w/v, gassed with 5 per cent carbon dioxide in oxygen and maintained at 39 C.
A helical strip cut from a thin-walled vessel,
such as a vein or small artery, presents certain
practical problems when contractions are recorded
by means of a lever writing on a smoked drum.
The mass of muscle contained in a thin strip is
small and the lowest tension acceptable with this
method' of recording (0.5 Gm.) is probably
greater than the optimum. As a result, the preparation appears greatly stretched and does not
exhibit an acceptable magnitude of contraction.
Such a strip tends to curl along its longitudinal
axis. A simple muscle holder was designed to
double the mass of tissue that might be contained
within the tissue bath and to reduee this tendency
to curl. The muscle strip was looped over a bar
and each end attached 0.5 cm. apart to the holder.
The attachment was by pressure along the entire
width of the strip. This bar, a short piece of
polyethylene tubing, was attached by silk thread
H E LARGE arteries and veins do more
than conduct blood to and from the heart.
They act as central, elastic, volume reservoirs.
Their walls contain vascular smooth muscle
under nervous 1 and humoral control 2 and also
many of the receptors that maintain homeostasis. The tone of this smooth muscle varies
in response to pharmacological and humoral
stimuli and, consequently, changes the activity of the associated volume or stretch receptors. 3 ' *
This paper presents a comparison of some
of the pharmacological parameters of the response to Z-epinephrine and Z-norepinephrine
shown by the smooth muscle of the large
arteries and veins in the rabbit. The results
of this comparison suggest that there is a
central group of vessels, both arteries and
veins, that contain smooth muscle in which
these parameters are identical. This smooth
muscle is more sensitive to Z-norepinephrine
than to Z-epinephrine. The smooth muscle of
other arteries and veins is less sensitive to
both these amines, but is more sensitive to
/-epinephrine than to Z-norepinephrinp.
Methods
The details of the experimental method, unless
otherwise stated, were similar to those previously
described by Bevan.5 A total of 30 rabbits of both
sexes, weighing 2.0 to 2.5 Kg., were used. Helically
cut vessel strips were prepared from 17 of the
largest- and medium-sized blood vessels of the
rabbit. The following parts of the vascular tree
were utilized: the whole of the braehial, facial,
main pulmonary, renal, and saphena arteries
and portal vein; the middle third of the common
carotid artery, the thoracic aorta, and the external
From the Department of Pharmacology, University
of California at Los Angeles Medical Center, Los
Angeles, California.
Supported by Grant H-4301 from the U. S. Public
Health Service.
Receiver! for publication January 23, 1961.
700
Circulation Research, Volume IX, May 1961
SENSITIVITY OF LARGE BLOOD VESSELS
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to the recording lever. The opposing surfaces of
the vessel were sufficiently separated to allow adequate circulation of the bath solution. Preliminary
experiments using standard strips from the thoracic aorta, showed that this method of mounting
the preparation did not significantly alter the
characteristics of the response to Z-epinephrine.
Tissues were allowed to equilibrate in the Krebs
saline solution two hours before use. Contractions
were then elicited simultaneously from all four
preparations every hour. When contractions were
completed, the tissues were washed and then rested
without tension until 20 minutes before the next
contractions were elicited. Contractions to Z-epinephrine and Z-norepinephrine were measured alternately. A minimum of four groups of measurements
(two of Z-epinephrine and 2 of Z-norepinephrine)
were made with each preparation. A total of at
least six responses to each drug was obtained for
each anatomically distinct vessel.
It has been shown that the maximum height of
contraction to Z-epinephrine may be calculated
from the responses to three successive submaxinial
doses of the drug.5 This calculation depends on
the previously shown fact" that experimental data
satisfactorily represented by the probit transformation, which is true of the aorta strip response
to Z-epinephrine, may be equally well fitted to the
logistical distribution. From this relationship, it
may be shown that if D is the drug concentration
producing a response, E, and A and B are constants, then if 1/E is plotted against D~B, a.
straight line is obtained with slope l/E max e A and
intercept 1/Emax. The value for B is determined
empirically by trial and error to give the best
straight-line fit. The relationship between E and
D is solved graphically to give E max . B is proportional to the slope of the dose-response curve.
The sensitivity or median effective dose is obtained
by extrapolation from a plot of logarithm dose
and probit response. With the aorta strip, it
has been shown that the maximum response to
Z-epinephrine calculated in this manner is the same
as the maximum response obtained experimentally
using a large dose, 1 mg. or more of the drug.
In these experiments, it was also confirmed that
this relationship held with Z-norepinephrine and
with helical preparations from other vessels.
The bitartrate salts of the levo-isomers of epinephrine and norepinephrine were used throughout these experiments. An inference of significance
was made when P < 0.05.
Results
The characteristics of response of 17 anatomically distinct vessels to Z-epinephrine and
/-norepinephrine were determined and compared with those obtained from the thoracic
Circulation Research, Volume IX. May 1961
701
aorta of the same animal at the same time.
Comparisons were made of the median effective dose, the slope of the logarithm doseprobit response curve, and the ratio of the
maximum heights of contraction to the two
amines. By this method, some of the causes of
variation, namely, that between individual
animals and that due to the length of survival of the muscle strip, were reduced to a
minimum. On the basis of these measurements, the vessels were divided into two
groups: (a) those in which these pharmacological characteristics were identical within
95 per cent confidence limits7 with those of
the thoracic aorta, and (b) a group in which
they differed. The results of these measurements are illustrated graphically in figure 1.
Vessels Containing Smooth Muscle with Pharmacological Characteristics Identical with Those of
the Thoracic Aorta
In these experiments, the mean median
effective dose of Z-epinephrine for the thoracic
aorta obtained three hours after the sacrifice
of the animal was 0.0330 /ig./ml. and that for
Z-norepinephrine was 0.0241 ^.g./ml. When the
median effective doses for Z-norepinephrine
and Z-epinephrine were compared in pairs
from the same animal, there was a significant
difference between them." The slopes of the
logarithm dose-probit response curves and the
maximum height obtained with the two sympathomimetic amines were identical. Within
95 per cent confidence limits, these parameters
when measured in the following vessels were
the same as in the thoracic aorta: abdominal
aorta; the femoral, main pulmonary, and
lobar pulmonary arteries; some of the preparations of the renal arteries; the external
jugular vein; and the inferior vena cava. The
smooth muscle of the common carotid and
saphena arteries was identical in all respects
except that the median effective dose of Z-norepinephrine was two to three times that for
the thoracic aorta. The median effective dose
for the smooth muscle of the external jugular
vein was identical with that of the aorta,
except that the slope of the logarithm doseprobit response curves for the response of the
vein to both amines was more steep.
702
BEVAN
FEMORAL
MAIN
li
AORTA
ABDOMINAL
ARTERY
PULMONARY
INFERIOR
VENA
EXTERNAL
RENAL
ARTERY
JUGULAR
VEIN
ARTERY
ARTERY
SAPHENA
ARTERY
PORTAL
. EPINEPHRINE
-I
ILIAC
1
1
1
BRACHIAL
1
ARTERY
ARTERY
. NOREPINEPMRINE
1
VEIN
COMMON
i
i
i
i
i
1i
li
il
!l
i
I
t
t
i
1
ARTERY
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POSTERIOR
ANTERIOR
CELIAC
ARTERY
CAVA
CAROTID
FACIAL
1
1
1
1
1
1
li
AORTA
PULMONARY
LOBAR
SLOPE
SENSITIVITY
VESSEL
THORACIC
MESENTERIC
MESENTERIC
ARTERY
-
1
i
l'i
i
i
i
ARTERY
i
i
1
ARTERY
1
C
M.E.D. VESSEL
2 3
S
i
10 20
M.E.D. THORACIC AORTA
M.E.D.THORACIC AORTA
i
-050
-025
0
S L O P E v e s s E L - SLOPE THOR.CC
AORTA
M.E.D.THORACIC AORTA
Figure 1
Summary of the sensitivity (median effective dose [M. E. D.]J and the slope of the doseresponse curve of the contractile response to \-norepinephrine and \-epinephrine in strips
prepared from various vessels of the rabbit. The thoracic aorta was used as a standard.
Vessels Containing Smooth Muscle with Pharmacological Characteristics Differing from Those of
the Thoracic Aorta
This group of vessels tested were less sensitive to Z-epinephrine and Z-norepinephrine
than the thoracic aorta, and, in contrast to
the previous group, were more sensitive
to Z-epinephrine than Z-norepinephrine. This
change was greatest in the ventral branches
of the abdominal aorta, the anterior and posterior mesenteric, and the celiac arteries (fig.
1). Some strips of the renal arteries had
properties similar to the thoracic aorta, others
different. These latter preparations showed a
greater sensitivity to Z-norepinephrine than
/-epinephrine. The slope of the logarithm doseprobit response curve for both amines was
significantly reduced in preparations from the
anterior and posterior mesenteric, celiac,
facial, and brachial arteries. This change of
slope was most marked with the celiae artery.
In figure 2, the logarithm dose-probit response curves are shown for the action of
Z-epinephrine and Z-norepinephrine on the
thoracic aorta and celiac artery of the same
animal. It shows that the smooth muscle of
the thoracic aorta is more sensitive to Znorepinephrine than Z-epinephrine, and that
the slopes of the dose-response curves are
parallel. The smooth muscle of the celiac
artery is less sensitive to both amines, particularly Z-norepinephrine, and the slopes of the
dose-response curves are more steep.
Discussion
This study suggests that there is a group
of the larger arteries and veins that contain
smooth muscle with the same parameters of response to Z-epinephrine and Z-norepinephrine :
namely, the thoracic aorta; the abdominal
aorta; the common carotid, femoral, main
pulmonary, lobar pulmonary, and saphena
arteries; some preparations of the renal arteries; the external jugular vein; and the
inferior vena cava. The other vessels tested,
the common iliac, brachial, facial, anterior
and posterior mesenteric and celiac arteries,
and the portal vein, are less sensitive and have
Circulation Research, Volume IX. May 1961
703
SENSITIVITY OF LARGE BLOOD VESSELS
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a steeper dose-response curve. "Whereas the
vessels of the first group are more sensitive to
Z-norepinephrine, those of the latter group are
more sensitive to Z-epinephrine.
The median effective dose is used as a
measurement of sensitivity. Consequently, the
sensitivity of vascular smooth muscle determined under the conditions of these experiments is independent of the magnitude of
contraction. Sensitivity is also independent of
tension.3 These differences in sensitivity may
not be correlated with vessel diameter, for the
femoral artery, although more sensitive than
the posterior mesenteric, is of smaller diameter. Neither may they be correlated with vessel-wall thickness, for the wall of the anterior
mesenteric artery is thicker and the sensitivitylower than the inferior vena cava, which contains smooth muscle with pharmacological
properties identical to that of the aorta. No
profitable conclusions may be drawn from a
comparison of the absolute response of the
smooth muscle from the different arterial
strips. The maximum height of response, but
not the sensitivity, is closely related to the
tension applied,3 but with these strips the
actual tension applied to the smooth muscle
is not known. The maximum response is dependent not only on the dimensions of the
tissue strips and the proportion of muscle
within their walls, but also on the orientation
of the fibers and the amount, type, and local
characteristics of the connective-tissue elements.
The embryonic cells that develop into the
smooth muscle of the tunica media of the
arterial and venous systems originate from
local mesenchyme.s The older concept9—that
most blood vessels develop as buds from the
aorta-has now been proved wrong. It is of
interest that the arteries and veins that
develop from the paired dorsal aortae, the
pharyngeal branchial arches, and the cardinal
veins, all closely associated in development,
tend to have the same sensitivity in the adult.
The vessels that contain smooth muscle derived
from mesoderm situated ventrally in the
embryo, the anterior and posterior mesenterie
and celiae arteries and the portal vein, have a
Circulation
Research,
Volume IX. May 10G1
THORACIC AORTA
& I EPINEPHRINE
O 1NOREPINEPHRINE
CEUAC ARTERY
A
•
/EPINEPHRINE
l.NOREPINEPHRINE
MICROGRAMS OF AMINE ADDED TO 45 ml. BATH
Figure 2
Relationship between contractile response and dose
of 1-norepinephrine and \-epinephrine in strips prepared from the thoracic aorta and celiae artery.
lower sensitivity than the preceding group.
The muscle of the umbilical artery is also
derived from ventral mesoderm, and in the
adult some of this muscle is incorporated in
the common iliac artery.10 This vessel has a
lower sensitivity than the vessels proximal and
distal to it, the abdominal aorta and the
femoral artery.
Changes in the mechanical properties of a
vessel wall modify the activity of associated
baro- or stetch receptors.11 All true pressoreceptors12'13 are found in the walls of the group
of vessels that from this study appear to be
most sensitive to the physiological amines.
Consequent^, pressoreceptor activity will be
affected by a wider range of amine levels than
if they were situated in peripheral and less
sensitive vessels.
Summary
Some of the pharmacological properties of
the smooth muscle of 17 anatomically different
vessels of the adult rabbit have been compared
using helical strips under in vitro conditions.
Using the median effective dose and the slope
of the logarithm dose-probit response curve
for Z-epinephrine and Z-norepinephrine as criteria, these vessels may be divided into two
groups. The vascular muscle of the thoracic
and abdominal aorta, the femoral, main pulmonary and lobar pulmonary arteries, some
BBVAN
704
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preparations of the renal arteries and the inferior vena cava exhibit, within 95 per cent
confidence limits, identical characteristics.
They are more sensitive to Z-norepinephrine
than £-epinephrine, and the slopes of the doseresponse curves to these amines are the same.
The muscle of the common carotid and
saphena arteries and the external jugular vein
is very similar to this group, but not identical.
The vascular muscle of the common iliac,
brachial, facial, anterior and posterior mesenterie, and celiac arteries, and the portal vein
is less sensitive, and the slope of the doseresponse curve more steep to these amines
than the previous group. They are more sensitive to Z-epinephrine than Z-norepinephrine
and the slopes of the dose-response curves for
these amines are not the same.
References
1. WECKMJN, N.: Local constriction and spasm of
large arteries elicited by hypotlialamic stimulation. Experientia 16: 34, 1960.
2. WIGGERS, C. J., AND WECRIA, E.: Active changes
in size and distensibility of the aorta during
acute hypertension. Am. J. Physiol. 124: 603,
1938.
3. ALEXANDER, B. S.: Influence of constrictor drugs
on the distensibility of the splanchnic venous
system analyzed on the basis of an aortic
model. Circulation Research 2: 140, 1954.
4.
HEYMANS, C, AND VAN DEN HEUVEL-HEYMANS,
G.: New aspects of blood pressure regulation.
Circulation 4: 581, 1951.
5. BEVAN, J. A.: Use of the rabbit aorta strip in
the analysis of the mode of action of Z-epinephrine on vascular smooth muscle. .T. Pharmacol. 129: 417, 1960.
6. FINNEY, D. J.: Statistical Method in Biological
Assay. New York, Hafner Publishing Co.,
1952.
7. DIXON, W. J., AND MASSEY, F. J.: Introduction
to Statisticiil Analysis, ed. 2. New York,
McGraw-Hill Book Co., Inc., 1957.
8. LE GROS CLARKE, W. E.: Tissues of the body,
ed. 4. Oxford, Clarendon Press, 1958.
9. BREJIER, J. L.: Development of the aorta and
aortic arches in rabbits. Am. J. Anat. 13:
11], 1912.
10. BAXTER, J. S.: Frazer 's Manual of Embroyology.
London, Bailliere, Tindall and Cox, 1953.
11. PETERSON, L. H.: Regulation of blood vessels.
Circulation 21: 749, .1960.
12.
AVIADO, D. M., JR., AND SCHMIDT, C. F . : Reflexes
from stretch receptors in blood vessels, heart
and lungs. Physiol. Rev. 35: 247, 1955.
13. Boss, J., AND GREEN, J. H.: Histology of the
common carotid baroceptor areas of the cat.
Circulation Research 4: 12, 3956.
Circulation Research, Volume IX, May 1901
Sensitivity of the Large Blood Vessels of the Rabbit to l-Epinephrine and l-Norepinephrine
JOHN A. BEVAN
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Circ Res. 1961;9:700-704
doi: 10.1161/01.RES.9.3.700
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Copyright © 1961 American Heart Association, Inc. All rights reserved.
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