Mechanism of enhanced Na-K-ATPase activity in cortical collecting duct from rats with nephrotic syndrome.

The maximal hydrolytic activity of Na-K-ATPase is specifically increased in the cortical collecting duct (CCD) of rats with puromycin-induced nephrotic syndrome (NS). This stimulation is independent of aldosterone and of endogenous ouabain-like substance. To investigate the mechanism responsible for this change, we compared the maximal Na-K-ATPase hydrolytic activity, the ouabain sensitive 86Rb influx, the specific [3H]ouabain binding, and the sensitivity of Na-K-ATPase to ouabain in the CCD of control rats and of rats given an intraperitoneal injection of puromycin 7 d before study. Both Na-K-ATPase activity and ouabain-sensitive 86Rb influx increased two-fold in rats with NS (ATPase activity: 34.1 +/- 2.1 vs. 18.0 +/- 0.7 pmol.mm-1 x min-1 +/- SE, n = 6, P < 0.001; Rb influx: 14.4 +/- 0.7 vs. 7.4 +/- 0.4 peq.min-1 +/- SE, n = 6, P < 0.001) whereas specific [3H]ouabain binding decreased in rats with NS (6.9 +/- 0.7 vs. 9.0 +/- 0.6 fmol.mm-1 +/- SE, n = 6, P < 0.005). Therefore, the maximal turnover rate of Na-K-ATPase increased over twofold in rats with NS (5,053 +/- 361 vs. 2,043 +/- 124 cycles.min-1 +/- SE, n = 6, P < 0.001). Analysis of the curves of inhibition of Na-K-ATPase by ouabain showed the presence of two Na-K-ATPase populations in both control and NS rats: a highly sensitive population (apparent Ki: 1.4 x 10(-6) M and 0.9 x 10(-6) M) and a less sensitive moiety (apparent Ki: 2.6 x 10(-4) M and 1.1 x 10(-4) M). The enhancement of Na-K-ATPase activity observed in the CCD of rats with NS was entirely due to the stimulation of the population of Na-K-ATPase with low ouabain sensitivity. These results suggest that a dysregulation of this subclass of Na-K-ATPase might be the primary cause of sodium retention in this model of nephrotic syndrome.

An inhibitor of sodium transport in the urine of dogs with normal renal function.

The urine and serum of chronically uremic patients and dogs contain an inhibitor of sodium transport that reduces short-circuit current (SCC) in the toad bladder and produces natriuresis in the rat. The present studies represent an effort to determine whether the same inhibitor is detectable in urine of normal dogs maintained on a dosium intake varying from 3 to 258 meq/day. Observations were made with and without fludrocortisone. The same Sephadex G-25 gel filtration fraction previously shown to contain the "uremic" inhibitor was tested in both the isolated toad bladder and rat bioassay systems. The fraction from dogs maintained on 258 meq qodium plus 0.2 mg fludrocortisone/day consistently inhibited SCC in the toad bladder and induced a natriuresis in the rat (P less than 0.001). The fraction from dogs on the same sodium intake without fludrocortisone was also natriuretic (P less than 0.01) but did not inhibit SCC significantly. In contrast, the fraction from dogs fed 3 meq sodium with fludrocortisone or 91 meq sodium without fludrocortisone had no significant effect in either assay system. Thus, an inhibitor of sodium transport has been found in the urine of nonuremic dogs. Both the degree of natriuresis in the rat and the degree of inhibition of SCC in the toad bladder correlated with the state of sodium balance which ensued in the dog.

Is phosphorylation of the alpha1 subunit at Ser-16 involved in the control of Na,K-ATPase activity by phorbol ester-activated protein kinase C?

The alpha1 subunit of Na,K-ATPase is phosphorylated at Ser-16 by phorbol ester-sensitive protein kinase(s) C (PKC). The role of Ser-16 phosphorylation was analyzed in COS-7 cells stably expressing wild-type or mutant (T15A/S16A and S16D-E) ouabain-resistant Bufo alpha1 subunits. In cells incubated at 37 degrees C, phorbol 12, 13-dibutyrate (PDBu) inhibited the transport activity and decreased the cell surface expression of wild-type and mutant Na,K-pumps equally ( approximately 20-30%). This effect of PDBu was mimicked by arachidonic acid and was dependent on PKC, phospholipase A(2), and cytochrome P450-dependent monooxygenase. In contrast, incubation of cells at 18 degrees C suppressed the down-regulation of Na,K-pumps and revealed a phosphorylation-dependent stimulation of the transport activity of Na,K-ATPase. Na,K-ATPase from cells expressing alpha1-mutants mimicking Ser-16 phosphorylation (S16D or S16E) exhibited an increase in the apparent Na affinity. This finding was confirmed by the PDBu-induced increase in Na sensitivity of the activity of Na,K-ATPase measured in permeabilized nontransfected COS-7 cells. These results illustrate the complexity of the regulation of Na,K-ATPase alpha1 isozymes by phorbol ester-sensitive PKCs and reveal 1) a phosphorylation-independent decrease in cell surface expression and 2) a phosphorylation-dependent stimulation of the transport activity attributable to an increase in the apparent Na affinity.

Insulin-induced stimulation of Na+,K(+)-ATPase activity in kidney proximal tubule cells depends on phosphorylation of the alpha-subunit at Tyr-10.

Phosphorylation of the alpha-subunit of Na+,K(+)-ATPase plays an important role in the regulation of this pump. Recent studies suggest that insulin, known to increase solute and fluid reabsorption in mammalian proximal convoluted tubule (PCT), is stimulating Na+,K(+)-ATPase activity through the tyrosine phosphorylation process. This study was therefore undertaken to evaluate the role of tyrosine phosphorylation of the Na+,K(+)-ATPase alpha-subunit in the action of insulin. In rat PCT, insulin and orthovanadate (a tyrosine phosphatase inhibitor) increased tyrosine phosphorylation level of the alpha-subunit more than twofold. Their effects were not additive, suggesting a common mechanism of action. Insulin-induced tyrosine phosphorylation was prevented by genistein, a tyrosine kinase inhibitor. The site of tyrosine phosphorylation was identified on Tyr-10 by controlled trypsinolysis in rat PCTs and by site-directed mutagenesis in opossum kidney cells transfected with rat alpha-subunit. The functional relevance of Tyr-10 phosphorylation was assessed by 1) the abolition of insulin-induced stimulation of the ouabain-sensitive (86)Rb uptake in opossum kidney cells expressing mutant rat alpha1-subunits wherein tyrosine was replaced by alanine or glutamine; and 2) the similarity of the time course and dose dependency of the insulin-induced increase in ouabain-sensitive (86)Rb uptake and tyrosine phosphorylation. These findings indicate that phosphorylation of the Na+,K(+)-ATPase alpha-subunit at Tyr-10 likely participates in the physiological control of sodium reabsorption in PCT.

Atrial natriuretic factor in patients with congenital heart disease: correlation with hemodynamic variables.

To investigate the alpha-atrial natriuretic factor in congenital cardiac malformations, three groups of children, aged 7 months to 16 years, with different hemodynamic situations were studied during routine cardiac catheterization. Twenty-one (group I) had tetralogy of Fallot, 24 (group II) had a left to right shunt with pulmonary hypertension and 12 (control group) had a minor cardiac lesion. Alpha-atrial natriuretic factor levels were determined by a radioimmunoassay on blood samples from the inferior vena cava, right atrium, pulmonary artery, left atrium and aorta. To evaluate the effect of an acute volume load, measurements of hormone and pressures were repeated after right ventriculography. Alpha-atrial natriuretic factor levels varied over a wide range in all groups and in all chambers investigated. Nevertheless, children with pulmonary hypertension had significantly higher levels of the hormone (p less than 0.01) and were well separated from the control group, but less well from those with tetralogy of Fallot. A 50% increase of alpha-atrial natriuretic factor from the inferior vena cava to the right atrium occurred in patients with shunt lesions with pulmonary hypertension and in patients with tetralogy of Fallot (p less than 0.001) and a further 30% increase from the right atrium to the pulmonary artery (p less than 0.05). After right ventriculography, a 100% to 200% increase of alpha-atrial natriuretic factor was observed in the total sample (p less than 0.001). A positive correlation was observed between right atrial mean pressure and right atrial alpha-atrial natriuretic factor (r = 0.63) and between pulmonary artery mean pressure and pulmonary artery alpha-atrial natriuretic factor (r = 0.61).(ABSTRACT TRUNCATED AT 250 WORDS)

Dual effects of suppressor of cytokine signaling (SOCS-2) on growth hormone signal transduction.

A family of suppressors of cytokine signaling (SOCS) has recently been identified of which two members have been shown to block growth hormone (GH) signaling. Dose-response experiments were conducted in 293 cells and SOCS-1 and SOCS-3 were shown to inhibit the transcriptional activation of a GH-responsive element and suppressed Jak2 tyrosine kinase activity. SOCS-2 had two opposite effects: at low concentrations it inhibited GH-induced STAT5-dependent gene transcription, but restoration of GH signaling was observed at higher concentrations. In cotransfection studies, SOCS-2 was able to block the inhibitory effect of SOCS-1 but not that of SOCS-3 on GH signaling. These findings suggest that a major function for SOCS-2 is to restore the sensitivity to GH by overcoming the initial inhibitory effects of other endogenous SOCS molecules.

Stimulation of ouabain-sensitive 86Rb+ uptake and Na+,K+-ATPase alpha-subunit phosphorylation by a cAMP-dependent signalling pathway in intact cells from rat kidney cortex.

We investigated in intact cortical kidney tubules the role of PKA-mediated phosphorylation in the short-term control of Na+,K+-ATPase activity. The phosphorylation level of Na+,K+-ATPase was evaluated after immunoprecipitation of the enzyme from 32P-labelled cortical tubules and the cation transport activity of Na+,K+-ATPase was measured by ouabain-sensitive 86Rb+ uptake. Incubation of cells with cAMP analogues (8-bromo-cAMP, dibutyryl-cAMP) or with forskolin plus 3-isobutyl-1-methylxanthine increased the phosphorylation level of the Na+,K+-ATPase alpha-subunit and stimulated ouabain-sensitive 86Rb+ uptake. Inhibition of PKA by H-89 blocked the effects of dibutyryl-cAMP on both phosphorylation and 86Rb+ uptake processes. The results suggest that phosphorylation by PKA stimulates the Na+,K+-ATPase activity.

Autoimmune hematologic diseases associated with infraclinical systemic lupus erythematosus in four patients. A human equivalent of the NZB mice.

In four patients with a diagnosis of autoimmune hemolytic anemia or idiopathic thrombocytopenic purpura antinuclear antibodies and circulating immune complexes (Clq-BA test) have developed at some time in their history. Renal biopsy material was assayed with different methods. Immunofluorescence studies revealed granular deposits of immunoglobulin G (IgG), immunoglobulin M (IgM) and third component of complement (C3). Upon optic microscopy, three patients had mild mesangial proliferation, one a focal glomerulonephritis. Upon electron microscopy, all patients exhibited mesangial and/or subendothelial deposits. The patients have been followed for 18 to 37 years since the beginning of their disease. There has been no clinical evidence of systemic lupus erythematosus (SLE), although they present in their glomeruli immunologic and anatomic features compatible with this disease. These patients seem to be a human equivalent of the black NZB mouse which presents immunohematologic disorders and some biologic markers of SLE without having a full clinical picture of SLE.

Improvement of drug-induced chronic renal failure in lung transplantation.

BACKGROUND: Nephrotoxicity is a frequently encountered adverse effect of calcineurin inhibitors (cyclosporine and tacrolimus)-combined immunosuppressive regimens. METHODS: We have compared the glomerular filtration rate in 14 patients who underwent lung transplantation, before and after replacement of azathioprine by mycophenolate mofetil and reduction of associated calcineurin inhibitors doses. RESULTS: After a mean follow-up of 16+/-4 months with the modified immunosuppressive regimen, the mean glomerular filtration rate increased by 20% with no change in lung function. CONCLUSION: By its strong immunosuppressive effect, mycophenolate mofetil allows the decrease of associated calcineurin inhibitor doses, with subsequent improvement of renal function without jeopardizing the transplanted lung.

Kinetics of cellular viability in warm versus cold ischemia conditions of kidney preservation. A biometric study.

We have determined the kinetics of the cellular viability ratio (CVR), defined as the number of living cells over the total cell count, in pig kidneys using propidium iodide and fluorescein diacetate staining, as a function of time and preservation conditions. The kidneys were preserved in warm or cold ischemia in order to mimic the conditions of transplantation from non-heart-beating donors or multiple removal with optimal preservation of the graft, respectively. To determine the CVR, the cells were obtained by a fine-needle aspiration biopsy, which minimizes the damage to the graft. A biometric analysis by regression enabled the determination of the time dependence for warm ischemia (CVR(t) = 80.0 x e(-0.733-t)(+2.7/-0.36)) and for cold ischemia (CVR(t) = 80.0 x e(-0.022-t)(+1.57/-0.64)) with a confidence interval of 95%. These master curves allow us to predict, under the described conditions, the CVR after a given ischemia time. The half-life of the cells can be deduced from the time-dependent CVR(t), and is 0.64 hr (38 min) for warm ischemia and 21.4 hr for cold ischemia. Further, the CVR for a given kidney can be used to assess its condition at removal: if the CVR is below 48% at 2 hr after removal, one can conclude that the organ has suffered a period of warm ischemia.

Mitochondrial anomalies in a Swiss family with autosomal dominant myoglobinuria.

We report on a Swiss family in which 10 individuals of both sexes in 4 successive generations suffered from myoglobinuria, precipitated by febrile illness. It is the second family described with autosomal dominant inheritance of myoglobinuria. Four individuals suffered acute renal failure, which in two was reversible only after dialysis. In a recent case, a mitochondrial disorder was suspected because of an abnormal increase in lactate levels during an exercise test and because of a subsarcolemmal accumulation of mitochondria in a muscle biopsy, associated with a lack of cytochrome C oxidase in some muscle fibers. No mutation in the mitochondrial DNA was identified. Along with the inheritance pattern, these findings suggest that the myoglobinuria in this family is caused by a nuclear-encoded mutation affecting the respiratory chain.

Very severe self-poisoning lithium carbonate intoxication causing a myocardial infarction.

A case of severe lithium carbonate self-poisoning is described, presenting with a very high serum lithium level (14.6 mmol/L) on admission. Lengthy and repeated hemodialyses were required to lower lithemia to nontoxic ranges. As is usually reported, our patient had prolonged neurologic manifestations (coma, hyperreflexia, fluctuating focal signs) and developed hypotension, cardiovascular collapse, nephrogenic diabetes insipidus, and diarrhea. Other less common features were the occurrence of acute myocardial infarction without coronary artery lesions and thrombocytopenia. The possible pathogenic mechanisms are discussed. Hemodialysis and supportive intensive care treatment are commented upon. The final outcome was favorable, and the patient recovered completely.

Atrial natriuretic factor after heart operations in children. Relation to hemodynamic and renal parameters.

The purpose of this study was to measure changes in serum atrial natriuretic factor concentrations immediately after heart operations in children under baseline conditions and in response to continuous infusion of dopamine (2.5 and 5.0 micrograms/kg/min). During control periods, levels of atrial natriuretic factor were elevated at 190 +/- 24 and 199 +/- 36 pg/ml. The cardiac index was 2.6 L/min/m2 and the renal plasma flow was decreased to 269 +/- 41 ml/min/1.73 m2, indicating a state of renal vasoconstriction (mean renal fraction of cardiac index of 10.0% +/- 1.0%). The mean sodium fractional reabsorption was 99.0% +/- 0.2%. During dopamine infusion, atrial natriuretic factor concentrations increased to 259 +/- 57 pg/ml and to 280 +/- 56 pg/ml, with dopamine 2.5 and 5.0 micrograms/kg/min, respectively (p = not significant), whereas left atrial pressure decreased from 11.7 +/- 0.9 mm Hg during the control period to 10.1 +/- 0.9 and to 9.9 +/- 1.0 mm Hg (p less than 0.05). No correlation was found between changes in left atrial pressure and atrial natriuretic factor levels. Dopamine at 5 micrograms/kg/min increased the cardiac index to 3.0 +/- 0.2 L/min/m2 (p less than 0.001) and the renal plasma flow to 406 +/- 61 ml/min 1.73 m2 (p less than 0.001), alleviating the renal vasoconstriction. The mean urinary sodium excretion increased to 0.33 +/- 0.08 mmol/kg/hr (p less than 0.01). The atrial natriuretic factor plasma concentrations were not related to the urinary sodium excretion, renal plasma flow, or glomerular filtration rate during the control period or during dopamine treatment. These data indicate that after heart operations in children, low urinary sodium excretion occurs despite high circulating atrial natriuretic factor levels. Atrial natriuretic factor concentrations were related neither to left atrial pressures nor to the renal changes induced by dopamine.

Changes in lipoproteins induced by the remnant kidney tissue or binephrectomy in chronic uremic patients treated by hemodialysis.

The role of the remmant kidney tissue in uremic patients undergoing hemodialysis treatment has rarely been considered to influence the changes in lipoprotein and lipid metabolism. Twenty hemodialyzed patients with remnant kidneys and 11 anephric patients were studied to examine whether the presence or the absence of remnant kidney leads to qualitative or quantitative changes of the lipids and lipoproteins. Anephric patients showed a significantly higher triglyceride level, 3.66 +/- 0.49 (SEM) mmol/L v 2.34 +/- 0.09 mmol/L in patients with remnant kidneys (P less than .01), higher very-low-density lipoprotein (VLDL) triglycerides, 1.24 +/- 0.30 mmol/L v 0.69 +/- 0.09 (P less than .04), and higher HDL-triglycerides, 1.22 +/- 0.29 mmol/L v 0.66 +/- 0.09 mmol/L (P less than .04). APO-AI was significantly decreased in anephric patients, 95.2 +/- 13.3 mg/dL v 129.7 +/- 6.02 mg/dL in patients with remnant kidneys (P less than .01). APO-B was similar in both groups. All APO-C and APO-E were significantly lower in anephric patients, APO-CI 6.13 +/- 0.87 mg/dL v 8.47 +/- 0.42 mg/dL in patients with remnant kidneys (P less than .01), APO CII 1.00 +/- 0.01 mg/dL v 10.0 +/- 0.01 mg/dL (P less than .0001), APO-CIII 10.12 +/- 1.43 mg/dL v 26.0 +/- 2.86 mg/dL (P less than .0005), and APO-E 8.0 +/- 0.02 mg/dL v 12.0 +/- 0.01 mg/dL (P less than .03). These results point out important differences between women and men. In women binephrectomy promotes a decreased concentration of all APO-C but has no influence on APO-AI concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal biopsy in SLE irrespective of clinical findings: long-term follow-up.

We analyzed data from 56 patients with Systemic Lupus Erythematosus (SLE) in whom renal biopsies were done systematically. The data taken into account for the study were: the histologic glomerular lesions at diagnosis, serum creatinine value, degree of proteinuria and qualitative urine sediment analysis at the time of biopsy, patient age at diagnosis and the evolution of renal function until the time the study was made. Therapy was prescribed according to the glomerular histologic lesion. The mean follow-up period from the time of the first biopsy was 8.2 years. At the time of the study, only 3 patients (5.3%) were on dialysis, while the rest of the patients (94.7%) had a satisfactory renal function. Our results indicate that systematic renal biopsy in SLE patients can furnish valuable data concerning the renal status whether there are clinical signs of renal involvement or not. Treatment based on the histologic images alone may considerably improve renal survival in SLE.

Glomerulonephritis associated with hepatitis B. report of a case and review of the literature.

A 45-year old developed membranoproliferative GN seven years after acute hepatitis. He was found to be a chronic carrier of HBsAg, and glomeruli contained granular deposits of immunoglobulins (Ig), complement (C) and HBsAg. Six months later, HN persisted, but HBsAg has disappeared from glomeruli; Ig and C were still present. It was concluded that GN was probably due to a hepatitis B associated antigen, but not necessarily to HBsAg.

[Digoxin-like natriuretic factor, raised during normal pregnancy, is increased in pregnancy-induced hypertension and pre-eclampsia]. / Le facteur natriurétique digoxin-like, augmenté dans la grossesse normale, est majoré dans l'hypertension induite par la grossesse et la prééclampsie.

UNLABELLED: The increase of peripheral resistance in pregnancy induced hypertension (PIH) and in preeclampsia (PE) is not yet explained since previous studies have found that renin-angiotensin-aldosterone system is actually depressed, that adrenergic system is inconstantly stimulated and that vasodilating prostaglandins are inconstantly decreased. In order to get a better insight in the pathogenesis of PIH and PE, we have measured the 24 h urinary excretion of digoxin-like natriuretic factor (DLF) in 15 normotensive pregnant women (NP), in 29 women with PIH and in 6 women with PE under normal salt diet, without treatment. DLF have been measured by radio receptor binding assay. Normal values were established in 14 normotensive non pregnant (NNP). In NP, 24 h urinary excretion of DLF was significantly higher than in NNP (respectively 14.9 +/- 7.5 and 9.5 +/- 2.5 nmol/mmol of creatininuria, p less than 0.01). Comparatively to NP, 24 h urinary excretion of DLF was significantly higher in PIH (31.7 +/- 19 nmol/mmol of creatininuria) and in PE (40.7 +/- 16.3 nmol/mmol of creatininuria). In PIH and PE, there were simultaneously a decrease of plasma renin activity and plasma volume but no difference for plasma catecholamines. IN CONCLUSION: 1. the production of DLF is increased by normal pregnancy; 2. it is increased in PIH and PE in comparison with NP and may explain the increase of peripheral resistance.

[Sequential study of the plasmatic atrial natriuretic factor and the urinary excretion of an ouabain displacing factor and of dopamine in normotensive pregnant women before and after labor]. / Etude séquentielle du facteur atrial natriurétique plasmatique et de l'excrétion urinaire d'un facteur déplaçant l'ouabaïne et de la dopamine chez la femme enceinte normotendue avant et après l'accouchement.

Estimation of urinary excretion of a ouabain displacing factor (ODF) and dopamine was carried out immediately before delivery, 7 days and 70-90 days after delivery in 12 normotensive pregnant women. Simultaneous estimation of plasma 99-126 atrial natriuretic factor (ANF), plasma renin activity (PRA) and plasma aldosterone were also undertaken. The data were compared with those obtained in a non pregnant normotensive group of women (n = 14) and a group of pregnant normotensive women in the early third trimester (n = 14). Urinary ODF and dopamine were significantly higher in the early third trimester when compared with non pregnant women but immediately before delivery, ODF excretion had fallen below non pregnant values and dopamine excretion had dropped to control values. Both remained low after delivery. Plasma ANF was higher in pregnant women when compared with non pregnant controls and remained high just before delivery and 7 and 70-90 days after delivery. PRA and plasma aldosterone were higher during pregnancy and had fallen to non pregnant values 7 days post-partum. It is concluded that there is considerable discrepancy in the evolution of natriuretic and antinatriuretic factors before and after delivery and that the drop of PRA and aldosterone by 7 days post-partum, contrasting with the unchanged high values of ANF, may contribute to negative sodium balance after delivery.

[Influence of chronic renal failure on the D-xylose test in man]. / Influence de l'insuffisance rénale chronique sur le test au D-xylose chez l'homme.

The aim of this study was to investigate the effect of chronic renal insufficiency on absorption, distribution and elimination of D-xylose which was chosen as a "test substance". Pharmacokinetic analysis was based on eighteen D-xylose tests carried out either by the enteral or parenteral route in a randomized fashion on nine patients suffering from chronic renal insufficiency. These results were compared with those obtained in healthy volunteers. The renal clearance was simultaneously measured with the 51Cr-EDTA test. In the experimental conditions the intestinal absorption of D-xylose was not modified qualitatively (absorption rate) nor quantitatively (systemic availability). Inspite of this, the maximal concentration of the D-xylose was higher in these patients and was reached later than in healthy volunteers. This fact should be taken into consideration when interpreting the results of a D-xylose test in patients suffering from chronic renal insufficiency.

[Evaluation of a method for determining the specific gravity of urine with a reagent strip]. / Evaluation de la méthode de détermination du poids spécifique des urines par une bandelette.

The performance of a new reagent strip method for determining the urine specific gravity was evaluated. 342 clinical specimens were assayed in duplicate by the new method and by the "falling drop" technique. The reproducibility (two lots of strips, four operators) was very good (96.2 per cent agreement between replicates within a range of 0,0100 specific gravity units). The correlation with the comparative method was satisfactory [81,2 per cent concordance within a range of 0,0100 specific gravity units]. No interference was found from ketones, blood or urobilinogen. The influence of proteins and glucose is discussed. The practical advantages of the new method are described.