Download cell physiology and electrolytes

Nephrology Dialysis Transplantation 29 (Supplement 3): iii69–iii72, 2014
doi:10.1093/ndt/gfu140
CELL PHYSIOLOGY AND ELECTROLYTES
SP001
OPTIMIZING THE ZS-9 POTASSIUM ION TRAP: PORE SIZE
AND THERMODYNAMICS
Alex Yang1, John J. Low2, Alejandro Leon3 and Henrik S. Rasmussen3
1
Xelay Acumen, Belmont, CA, 2Consultant, Schaumburg, IL, 3ZS Pharma, Inc.,
Coppell, TX
Introduction and Aims: Physiologic ion channels take advantage of the different ionic
diameters to selectively filter the requisite ion. For example, although potassium (K+)
and sodium (Na+) ions are similar in size (3.0 Å and 2.3 Å, respectively [Volkov
1997]), K+ channels discriminate between K+ and Na+ by a factor of 10,000 (Doyle
1998) using a selectivity filter. To pass through the selectivity filter, an ion must first
shed its coat of water and interact with the carbonyl oxygens. Although the K+ channel
filter can accommodate both K+ and Na+ ions, only K+ ions are large enough to
interact with the carbonyl oxygens after dehydration. Zirconium silicates have been
known to extract ammonium ions from streams (Bem 1999). Since ammonium and K+
cations have similar radii, it suggests that zirconium silicates may be effective in
capturing K+. An optimization process was undertaken to find a zirconium silicate
drug candidate to capture K+ cations in a specific manner. Several lattice structures of
zirconium silicates were tested to find one that mimicked the action of physiologic K+
channels. The result of this optimization process was ZS-9, a material designed and
engineered to preferentially entrap K+ ions after oral administration. Results from a
structural study to determine the pore size of ZS-9 and thermodynamic stability
modeling for various cations (Na+, K+, calcium [Ca2+], and magnesium [Mg2+])
within the ZS-9 lattice structure are reported here.
Methods: In the structural study, ZS-9 was dried and ground in an agate mortar, then
placed into a powder diffractometer. Data were collected at room temperature with
monochromated Cu α1 radiation (λ=1.5406 Å). Rietveld least squares structural
refinements were performed, and the interatomic distances were calculated from the
resulting atom positions. The size of the pore opening was calculated by subtracting
twice the atomic radius of oxygen (van der Waals radius, r=1.52 Å) from center-center
interatomic distances. For the thermodynamic stability modeling, the predicted
energies for different cation forms of ZS-9 (ie, Na-ZS-9, K-ZS-9, Ca-ZS-9 and
Mg-ZS-9) and alkali and alkaline earth oxides from models were used to estimate the
cation exchange energies in ZS-9. All energies were computed relative to the Na+ form
of ZS-9, defined as the reference state.
Results: The structure of ZS-9 consists of units of octahedrally and tetrahedrally
coordinated zirconium and silicon atoms with oxygen atoms acting as bridges between
the units, forming an ordered cubic lattice structure. The framework is negatively
charged due to the octahedral [ZrO6]-2 units. The pore opening of ZS-9 is composed
of an asymmetrical seven-member ring (Figure) with an average size of ~3 Å.
Thermodynamically, ZS-9 with K+ was calculated to be more stable than ZS-9 with Na+,
Ca2+, or Mg2+. For example, the K+ form of ZS-9 was 20 kcal/mol more stable than the
Na+ form.
Conclusions: The diameter of the unhydrated K+ ion is similar to that of the ZS-9 pore
opening, indicating the K+ cations can fit within the lattice structure of ZS-9 after they
shed their hydration shell, which confers ZS-9 high specificity for K+ ions. This
SP001
hypothesized mechanism of action is supported by results from the thermodynamic
study, which demonstrates the selectivity of ZS-9 for K+ over other ions.
SP002
EFFECT OF VASOPRESSIN ANTAGONISM ON RENAL
HANDLING OF SODIUM AND WATER AND CENTRAL AND
BRACHIAL BLOOD PRESSURE DURING INHIBITION OF
THE NITRIC OXIDE SYSTEM IN HEALTHY SUBJECTS
Safa Al Therwani1
University Clinic In Nephrology and Hypertension and Aarhus University,
Holstebro, Denmark
1
Introduction and Aims: Tolvaptan is a selective vasopressin receptor antagonist
(V2R) that increases free water excretion. We wanted to test the hypotheses that
tolvaptan changes both renal handling of water and sodium and systemic
hemodynamics during basal conditions and during nitric oxide (NO)-inhibition
with L-NG-monomethyl-arginine (L-NMMA).
Methods: Nineteen healthy subjects were enrolled in a randomized,
placebo-controlled, double-blind, crossover study of two examination days. Tolvaptan
15 mg or placebo was given in the morning . L-NMMA was given as a bolus followed
by continuous infusion during 60 minutes. We measured urine output(OU), free water
clearance (CH2O), fractional excretion of sodium (FENa), urinary aquaporin-2
channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma vasopressin
( p-AVP), central and brachial blood pressure(cBP, bBP).
Results: During baseline conditions, tolvaptan caused a significant increase in UO,
CH2O and p-AVP, and FENa was unchanged. During L-NMMA infusion, UO and
CH2O decreased more pronounced after tolvaptan than after placebo (-54 vs.-42%
and -34 vs.-9% respectively). U-AQP2 decreased during both treatments, whereas
u-ENaCγ decreased after placebo and increased after tolvaptan. CBP and bBP were
unchanged.
Conclusions: During baseline conditions, tolvaptan increased renal water excretion.
During NO-inhibition, the more pronounced reduction in renal water excretion
after tolvaptan indicates that NO promotes water excretion in the principal cells, at
least partly, via an AVP-dependent mechanism. The lack of decrease in u-AQP2 by
tolvaptan could be explained by a counteracting effect of increased plasma
vasopressin. The antagonizing effect of NO-inhibition on u-ENaC suggests that NO
interferes with the transport via ENaC by an AVP-dependent mechanism.
SP003
THE HIDDEN MESSAGE OF URINE: IN-DEPTH
CHARACTERIZATION OF THE HEALTHY URINARY
PROTEOME
Maurizio Bruschi1, Laura Santucci1, Marco Bonsano1, Giovanni Candiano1,
Gian Marco Ghiggeri1 and Enrico Verrina1
1
Istituto Giannina Gaslini, Genova, Italy
Introduction and Aims: Urine is a biological fluid resulting from the filtration of
blood, is in close proximity to several organs and tissues, and its collection is non
invasive and readily available. In this context, this body fluid has historically
represented a particularly interesting source of kidney disease biomarkers.However, as
in the case of other biological fluids, one of the main analytical challenges in the
characterization of urinary proteome is the very wide concentration range of proteins,
largely exceeding the dynamic range of current analytical approaches.
Methods: Here, we described an extensive sub-fractionation method to investigate the
characterization of the healthy urinary proteome. After the collection, urine samples
are centrifuged to remove cells and debris and then are ultra-centrifuged in order to
pellet the micro-vesicles. The supernatant is treated with a mixture of organic solvents
to pellet the highly hydrophobic proteins and remove the interference of pigments.
This supernatant is dialysed and loaded on Combinatorial Peptides Ligand Library
(CPLL) to reduce the dynamic range of protein concentration in urine and at the same
time unmask previously undetected proteins. Finally, each urinary fraction is processed
using two-dimensional electrophoresis and mass spectrometry techniques, and the
qualitative and quantitative data are analyzed using the hierarchical clustering analysis.
Results: The combined use of this proteomic approach has allowed us to create a
“complete” virtual map of the healthy urinary proteome, identifying a total of 3429
proteins. In addition, the particular chemical and physical characteristics of this
sub-fractionation method allowed to highlight: 744 proteins in micro-vesicles, 85
proteins in the extraction with organic solvents, and 695 proteins in CPLL, all unique
to each fraction.
Conclusions: These proteins may represent new potential biomarkers of organ
function and/or disease.
© The Author 2014. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.
Abstracts
Nephrology Dialysis Transplantation
The next step of this study will consist in applying this sub-fractionation method to the
characterization of urinary proteome of patients affected by different kidney diseases in
order to identify new disease biomarkers of potential diagnostic and prognostic value.
SP004
ACQUIRED BARTTER SYNDROME DUE TO STREPTOMYCIN
Shankar Prasad Nagaraju1, Dilip Ashok Kirpalani2, Gaurav Daga2, Hardik Shah2,
Aditya S Bhabhe2 and Ashok L Kirpalani2
1
Kasturba Medical College, Manipal University, Manipal, India, 2Bombay Hospital
and Medical Research Centre, Mumbai, India
specificity was 39%. The positive predictive value (PPV) and negative predictive value
(NPV) were 42% and 96%, respectively (Table 1). The sensitivity of SID for metabolic
alkalosis was 45% and specificity was 56%. The PPV and NPV were 89% and 69%,
respectively (Table 2).
Conclusions: Finally, [SID] and [HCO3-] centered models investigated with respect to
their consistency with each other in this study. It seems that SID values of less than 38
mmol/L is not reliable for detecting metabolic acidosis, based upon PPV. However, SID
values of more than 40 mmol/L may be used for diagnosing metabolic alkalosis cases,
considering PPV obtained in the study.
SP005
Introduction and Aims: Bartter syndrome is an autosomal recessive renal tubular
disorder characterized by hypokalemia, metabolic alkalosis, hypocalcaemia,
hypomagnesaemia and hypercalciuria.
Pseudo- Bartters/acquired Bartters syndrome has been commonly reported with
diuretic abuse and laxative abuse. Among aminoglycosides, it has been described with
gentamycin in few case reports. We report a case with similar conglomeration of
electrolyte imbalance, but in an unusual setting with streptomycin.
Methods: Case report
Results: A 74 year old lady who is a known case of diabetes mellitus, hypertension, and
hypothyroidism was recently found to have tubercular pleural effusion. She was started
on antituberculous treatment which included streptomycin. Two weeks later, she
developed convulsions and involuntary movements. On evaluation, she had
hypokalemia, hypomagnesemia, hypocalcemia and metabolic alkalosis which persisted
even after replacement therapy(Table 1). Urine analysis showed TTKG > 20 and
24 hour urine analysis confirmed the loss of potassium, magnesium and calcium in
urine.After discontinuing streptomycin, she showed marked recovery over a week in
her electrolyte abnormalities and alkalosis(Table 2).
Conclusions: Ours is a rare case report of renal electrolyte wasting that mimicked
Bartter syndrome and was induced by streptomycin.Thus while using aminoglycosides
it should be kept in mind that they not only cause acute kidney injury but also can
cause serious electrolyte disturbances in the form of pseudobartter’s syndrome.
SP005
SENSITIVITY AND SPECIFICITY OF STRONG ION
DIFFERENCE IN DETECTING METABOLIC ACIDOSIS
AND ALKALOSIS CASES DETERMINED BY BICARBONATE
BASED MODEL
SP005
Hakan Sarlak1, Fatih Bulucu1, Muharrem Akhan1, Seref Demirbas1,
Mustafa Cakar2 and Levent Yamanel1
1
Gulhane Military Medical Academy, Ankara, Turkey, 2Eskisehir Military Hospital,
Eskisehir, Turkey
Introduction and Aims: The Strong Ion Difference (SID) is the difference between the
sums of concentrations of the strong cations and strong ions ([SID] = [Na+] + [K
+] + [Ca+2] + [Mg+2] - [Cl-] - [Other Strong Anions]). With normal protein levels,
[SID] is about 38-40 mmol/L. The traditional approach to acid-base balance is based
on bicarbonate [HCO3-] levels. In this study, we aimed to investigate the sensitivity
and specificity of SID in detecting metabolic acidosis and alkalosis cases diagnosed by
traditional model.
Methods: A total of 493 blood gas measurements included into the study. The
measurements were obtained retrospectively from subjects monitored in intensive care
unit and internal medicine clinics. If the SID &lt 38 mmol/L and SID &gt 40 mmol/L
were considered as metabolic acidosis and alkalosis, respectively.
Results: Hundred fifty-six of the measurements were metabolic acidosis and 218
metabolic alkalosis. The sensitivity of SID for metabolic acidosis was 96% and
SP004 Table 1. Persistent electrolyte disturbances on streptomycin
Metabolic parameters
Na+(m eq/L)
K+(m eq/L)
Cl-(m eq/L)
HCO3-(m eq/L)
Ca++( mg/dl)
PO4( mg/dl)
Mg++( mg/dl)
Day 1
138
2.1
88
38
5
0.8
0.3
Day 2
131
2.9
93
35
5.3
0.7
0.5
Day 3
134
3.1
96
32
6.3
1
1
Day 4
137
2.6
100
33
6.04
1.2
1
Day 5
142
3.4
106
33
5.7
1
1.2
Day 6
140
2.7
109
34
4.5
1
1.3
Day 7
142
2.9
106
38
5.1
1.2
1.1
SP006
ACID-BACE DISORDER AFTER ORTHOTOPIC BLADDER
REPLACEMENT: ILEAL NEOBALDDER COMPARED WITH
ILEAL CONDUIT
Younhg-Ki Lee1, Seung Min Lee1, Ajin Cho1, Jwa-Kyung Kim1, Myung-Jin Choi1,
Dong-Ho Shin1, Jong-Woo Yoon1, Ja-Ryong Koo1, Hyung Jik Kim1,
Jung-Woo Noh1 and Young Goo Lee1
1
Hallym University College of Medicine, Seoul, Republic of Korea
Introduction and Aims: Radical cystectomy with urinary tract reconstruction is the
standard treatment for invasive bladder cancer. Several investigators have reported the
frequent incidence of normal anion gap metabolic acidosis and electrolyte disturbance
in those patients. We analyzed the pattern of metabolic acidosis and hypokalemia in
SP004 Table 2. Improvement of electrolyte disturbances after stopping Streptomycin
Metabolic parameter
Na+(meq/L)
K+(meq/L)
Cl- (meq/L)
HCO3-(meq/L)
Ca++(mg/dl)
PO4(mg/dl)
Mg++ (mg/dl)
iii | Abstracts
Day 8
137
2.5
102
39
4.3
1.6
1.1
Day9
144
2.7
101
46
5.6
1.7
1
Day 10
143
3.6
103
33
7.1
3
1.6
Day 11
139
3.3
102
34
7.8
3.3
1.8
Day 12
134
4
100
28
7.7
3.6
1.9
Day 13
135
4
98
25
7.2
3.2
2
Day14
137
3.7
102
26
7.3
4
2
Volume 29 | Supplement 3 | May 2014
Abstracts
Nephrology Dialysis Transplantation
patients following the construction of an ileal neobladder compared with ileal conduit
method, and searched for the risk factors affecting metabolic acidosis.
Methods: Sixty-seven patients who underwent radical cystectomy and urinary
diversions for invasive bladder cancer were analyzed. Patients with any illness such as
severe pulmonary disorder or taking any medication that could lead to metabolic
acidosis were excluded. Acid-base balance, serum electrolytes, renal function and
effects of renal function on acid-base metabolism were compared in patients with ileal
neobladder and ileal conduit.
Results: The urinary diversions were performed using ileal neobladder for 41 patients
or ileal conduit for 26 patients. No significant differences were observed in their
baseline characteristics and preoperative variables examined between the ileal
neobladder and ileal conduit groups, except for age. Metabolic acidosis was detected in
16 patients (39.0%) with ileal neobladder and in 6 patients (23.1%) with ileal conduit.
Metabolic acidosis with normal anion gap occurred more often in ileal neobladder
group (9 patients, 22.0%) than ileal conduit group (1 patient, 3.8%), however the
differences were not statistically significant. The close association between the serum
creatinine level and total CO2 (P<0.01, r=-0.249) were demonstrated. Acute kidney
injury and all-cause mortality were frequent in patients with metabolic acidosis,
especially ileal neobladder group. Postoperative hypokalemia in both groups showed no
differences in statistically significance.
Conclusions: Patients with ileal neobladder tended to develop metabolic acidosis with
normal anion gap more frequently than those with ileal conduit, but there was no
statistical significance. The degree of metabolic acidosis was closely associated with the
renal function.
SP007
SP007 Figure 2: Rapidly normalized serum Na despite fluid liberalization and a single
oral dose of 15 mg Tolvaptan.
SEVERE SYMPTOMATIC ACUTE HYPONATREMIA IN
TRAUMATIC BRAIN INJURY RESPONDS VERY RAPIDLY TO A
SINGLE 15 MG DOSE OF ORAL TOLVAPTAN: A MAYO CLINIC
HEALTH SYSTEM HOSPITAL EXPERIENCE - NEED FOR
CAUTION WITH TOLVAPTAN IN YOUNGER PATIENTS WITH
PRESERVED RENAL FUNCTION
Macaulay Onuigbo1 and Nneoma Agbasi2
1
Mayo Clinic, Rochester, MN, USA & Mayo Clinic Health System, Eau Claire, WI,
USA, Eau Claire, WI, 2North East London NHS Foundation Trust, United Kingdom,
London, United Kingdom
Introduction and Aims: Hyponatremia is common and affects up to 30% of
hospitalized patients. In traumatic brain injury, it results from either SIADH or from
cerebral salt wasting. Tolvaptan is now well established as a potent pharmaceutical
agent to treat symptomatic hyponatremia from SIADH. Over rapid correction is
dangerous. We describe the dramatic correction of serum Na by 18 mEq/L over
18 hours after a single 15 mg dose in a young man with normal kidney function (eGFR
of 126).
Methods: Case report.
Results: A 32-year old Caucasian male was admitted to the Trauma Service after a
motor vehicle accident. He had altered level of consciousness, acute right posterior
11th and 12th rib fractures, large scalp hematoma, and a small subarachnoid
hemorrhage. His serum Na quickly fell from 141 mEq/dL to 121 mEq/dL over several
days. despite corrective measures (Figure 1). Nephrology was consulted. Symptoms
included blurred vision, poor memory and cognitive impairment. Tolvaptan 15 mg
single dose was administered. Fluid intake was liberalized. Soon after, he noticed
increased urination, increased thirst and he was soon drinking “tons of water”. Serum
Na rapidly increased to 139 mEq/dL over 18 hours (Figure 2). His urine output more
than quintrupled (Figure 3). AVP level was 1.4 pg/mL, consistent with SIADH. Two
days later, the symptoms had fully resolved. At post-hospitalization, serum Na was
139 mEq/dL (Figure 4).
Conclusions: Previous studies on Tolvaptan recruited older patients, 64-67 years, with
some renal impairment. Tolvaptan doses were 30 mg daily dose or higher. The very
rapid correction in our 32-year old male patient, the first such report in the literature, is
SP007 Figure 3: Quintrupling of urine output following a single oral dose of 15 mg
Tolvaptan.
SP007 Figure 4: Normalized serum Na 11 days following a single oral dose of 15 mg
Tolvaptan.
the result of young age and normal kidney function. We suggest the use of lower doses
of Tolvaptan (15 mg or lower) in younger patients with preserved kidney function.
SP008
PLASMAPHERESIS IMPROVES THE OUTCOME OF OSMOTIC
DEMYELINATING SYNDROME
Koike Minako1, Kumon Saeko1, Usui Ryosuke1, Kuzuhara Shinzo1 and
Onitsuka Sirou1
1
Japan, Chiba, Japan
SP007 Figure 1: Falling Serum Na despite fluid restriction, oral Na tablets and reported
infusions of 30% sailing boluses.
Volume 29 | Supplement 3 | May 2014
Introduction and Aims: Rapid correction of serum sodium is known to be associated
with central pontine myelinolysis(CPM). Currently, there is no standard therapy for
CPM other than supportive therapy. Other therapy includes steroid, plasmapheresis
and IVIG, but these therapies have not been shown to be particularly effective.
doi:10.1093/ndt/gfu140 | iii
Abstracts
Methods: A 71-year-old woman became lethargic and was admitted to hospital. Blood
tests revealed severe hyponatremia(101mEq/l) that was adjusted over three days to
120mEq/l by infusing saline. Then the patient’s consciousness rapidly deteriorated
again. Neurological examination disclosed palsy with tetraplegia associated with
deep-tendon hyperreflexia. Magnetic resonance imaging(MRI)performed an area of
hyperintensity in the central pons on T2-weighted images suggestive of CPM.
Results: Six consecutive therapeutic plasmapheresis sessions were started with two to
three sessions a week. Significant clinical improvement began after plasmapheresis.
Two months later, she became remarkably better, started to speak, and moved her
extremities upon request.
Conclusions: We successfully treated patients with extensive therapeutic
plasmapheresis soon after the diagnostic confirmation of CPM.
SP009
URINARY EXCRETION OF AQP2 AND ENAC DURING
AMILORIDE AND THIAZIDE TREATMENT IN HEALTHY
HUMANS. A RANDOMIZED, PLACEBO-CONTROLLED TRIAL
Janni Jensen1,2, Frank H Mose1, Anna-Ewa O Kulik1, Jesper N Bech1 and
Erling B Pedersen1,2
1
Regional Hospital Jutland West, Holstebro, Denmark, 2Aarhus University,
Aarhus, Denmark
Introduction and Aims: Urinary excretion of aquaporin2 (u-AQP2) and the γ-fraction
of epithelial sodium channels (u-ENaCγ) are used to evaluate the water transport via
aquaporin-2 water channels (AQP2) and sodium transport via epithelial sodium
channels (ENaC) in the principal cells in the distal nephron. We wanted to test the
hypothesis that the functional state of AQP2 and ENaC in healthy humans change,
iii | Abstracts
Nephrology Dialysis Transplantation
both at baseline and after 3 % hypertonic saline, while inhibiting the sodium chloride
cotransporter (NCC) with thiazide or ENaC with amiloride.
Methods: In a randomized, double-blinded, placebo-controlled, crossover study,
23 healthy subjects on a standardized diet, regarding calories, sodium and fluid, were
studied. The subjects recieved amiloride 5 mg, thiazide 1.25 mg or placebo twice a day
for 5 days before each examination day. At baseline and after an infusion with
3% hypertonic saline, we measured urinary concentrations of u-AQP2, u-ENaCγ,
glomerular filtration rate (GFR) estimated by 51Cr-EDTA clearance, free water
clearance (CH2O), fractional excretion of sodium (FENa) and potassium (FEK),
plasma concentrations of sodium ( pNa) and potassium ( pK), vasopressin ( pAVP),
renin (PRC), Angiotensin II ( pANG II), Aldosterone ( pAldo), brachial blood pressure
(bBP) and central blood pressure (cBP) estimated by applanation tonometry and
extracellular volume (ECV) using bioimpedance spectroscopy technique.
Results: At baseline, there were no differences in u-AQP2, u-ENaCγ or 24-h bBP. Both
thiazide and amilorid increased PRC, pAng II and pAldo and decreased ECV.
Amiloride increased FENa and pK, while pNa decreased. Thiazide decreased CH2O,
pNa and pK. After hypertonic saline, u-AQP2 increased during placebo and amilorid,
but not during thiazide. In addition, CH2O decreased less during thiazide compared to
amilorid and placebo. U-ENaC and FENa increased in all three groups. PRC, AngII
and p-Aldo decreased to the same extent, while AVP increased, but to a significant
smaller degree during thiazide. ECV and bSBP increased slightly in all three groups,
while thiazide decreased bDBP and cDBP.
Conclusions: The study documents that in healthy humans, volume expansion with
3% hypertonic saline, result in a lower reabsorption of water via AQP2 during thiazide
compared to amilorid and placebo. This might be due to a reduced stimulation of AVP
on receptors located in the basolateral membrane of the principal cell. The increase in
u-ENaCγ might be compensatory phenomena to counteract a decreased reabsorption
of sodium in proximal tubules.
Volume 29 | Supplement 3 | May 2014