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The purpose of this study was to determine whether there is a correlation between phosphorylation and activity of the epithelial sodium channel (ENaC). The three subunits that form the channel were immunoprecipitated from A6 cells by using specific polyclonal antibodies after labeling cells with (35)S or (32)P. When immune complexes were resolved on SDS-PAGE, the alpha-subunit migrated at 85 and 65 kDa, the beta-subunit at 115 and 100 kDa, and the gamma-subunit at 90 kDa. In the resting state all three subunits were phosphorylated. The alpha-subunit was phosphorylated only in the 65-kDa band, suggesting that the posttranslational modification that gives rise to the rapidly migrating form of alpha is a requirement for phosphorylation. Stimulation with 100 nM insulin for 30 min increased phosphorylation of alpha-, beta-, and gamma-subunits approximately twofold. Exposure to 1 microM aldosterone for 16 h increased protein abundance and phosphorylation proportionately in the three subunits. When insulin was applied to cells pretreated with aldosterone, phosphorylation was also increased approximately twofold, but the total amount of phosphorylated substrate was larger than in control conditions because of the action of aldosterone. This result might explain the synergistic increase in sodium transport under the same conditions. The protein kinase C inhibitor chelerythrine abolished insulin effects and decreased sodium transport and subunit phosphorylation. Together, our findings suggest that ENaC activity is controlled by subunit phosphorylation in cells that endogenously express the channel and the machinery for hormonal stimulation of sodium transport.

Unlabelled: In this prospective, randomized, placebo-controlled, double-blinded study, we determined the effects of two commonly used adjuncts, mannitol and dopamine, on beta(2)-microglobulin (beta(2)M) excretion rates in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass (CPB). beta(2)M excretion rate has been described as a sensitive marker of proximal renal tubular function. One-hundred patients with a preoperative serum creatinine level

There are conflicting reports in the literature regarding the adenosine receptor that mediates the increase in sodium transport in the A6 cell. In this study we used specific A1 and A2 adenosine receptor agonists and antagonists, as well as two different subclones of the A6 cell, to determine which adenosine receptor mediates the increase in sodium transport. In the A6S2 subclone, basolateral and apical N6-cyclohexyladenosine (CHA), a selective A1 receptor agonist, stimulated sodium transport at a threshold concentration <10(-7) M, whereas CGS-21680, a selective A2 receptor agonist, had a threshold concentration that was at least 10(-5) M. The A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) was found to have a nonspecific effect on CHA-stimulated sodium transport, whereas the A2 receptor antagonist 8-(3-chlorostyryl)caffeine (CSC) had no effect. As with the A6S2 subclone, basolateral and apical CHA stimulated sodium transport at a nanomolar concentration in the A6C1 subclone and the threshold concentration for CGS-21680 was in the high micromolar range. Concurrent with the increase in 1 receptor in different subclones of the A6 cell, including a subclone capable of anion secretion.

The natriuretic effect of Ca(2+) channel blockers has been attributed to hemodynamic changes and to poorly defined direct tubular effects. To test the possibility that verapamil may inhibit Na(+) reabsorption at the distal tubule, its effect on transepithelial Na(+) transport in aldosterone-stimulated A6 cells was determined. Cells were grown on permeable supports, and short-circuit current (I(sc)) measured in an Ussing chamber was used as a surrogate marker for transepithelial Na(+) transport. Application of 300 microM verapamil to the apical side inhibited I(sc) by 77% and was nearly as potent as 100 microM amiloride, which inhibited I(sc) by 87%. Verapamil-induced inhibition of I(sc) was accompanied by a significant increase in transepithelial resistance, suggesting blockade of an apical conductance. Its action on transepithelial Na(+) transport does not appear to occur through inhibition of L-type Ca(2+) channels, since I(sc) was unaffected by removal of extracellular Ca(2+). Verapamil also does not appear to inhibit I(sc) by modulating intracellular Ca(2+) stores, since it fails to inhibit transepithelial Na(+) transport when added to the basolateral side. The effect on Na(+) transport is specific for verapamil, since nifedipine, Ba(2+), 4-aminopyridine, and charybdotoxin do not significantly affect I(sc). A direct effect of verapamil on the epithelial Na(+) channel (ENaC) was tested using oocytes injected with the alpha-, beta-, and gamma-subunits. We conclude that verapamil inhibits transepithelial Na(+) transport in A6 cells by blocking ENaC and that the natriuresis observed with administration of verapamil may be due in part to its action on ENaC.

This report includes cases of hyponatremia in preeclampsia. Two patients were identified with preeclampsia complicated by hyponatremia, one with and the other without nephrotic syndrome. Together with 3 cases of hyponatremia recently reported, these additional cases from the same geographic area suggest that hyponatremia is not a rare complication of preeclampsia.

Objective: The objective of this report is to describe a defect in water metabolism, characterized by hyponatremia, in patients with pre-eclampsia-induced nephrotic syndrom., Study Design: This was an observational study of 3 women., Results: Hyponatremia was observed in 3 women with pre-eclampsia characterized by various extrarenal manifestations, as well as by nephrotic syndrome with normal or nearly normal renal function. Restriction in water intake partially corrected hyponatremia before delivery in each case, and no complications were observed in the neonates. The mechanism of impaired excretion of water in these patients is proposed to involve persistent and inappropriate production of vasopressin through stimulation of the nonosmotic mechanism for vasopressin secretion in response to a reduction in effective plasma volume., Conclusions: These results indicate for the first time that women with pre-eclampsia are, at least when nephrotic, at risk for development of dilutional hyponatremia, which can cause neurologic complications that simulate those of eclampsia.

Background: Traditional protein kinase assays include the use of [32P] labeled ATP as phosphate donor and a substrate protein or peptide as phosphoreceptor. Since this approach has a number of drawbacks in addition to generating ionizing radiation, several non-isotopic methods have been developed. Although shown to reflect the activity of purified enzymes, none have been demonstrated to detect physiological changes in endogenous enzyme activity in cell homogenates., Methods: Studies were performed to examine the kinetics, reproducibility, and optimal assay conditions of a novel non-radioisotopic kinase assay that detects PKA activity by phosphorylation of the peptide substrate Kemptide covalently bound to a fluorescent molecule (f-Kemptide). Basal and agonist-induced PKA activity in epithelial cell homogenates was measured., Results: The kinetics of f-Kemptide were similar to the standard radioisotopic method with intraassay and interassay variations of 5.6 +/- 0.8% and 14.3 +/- 2.6%, respectively. Neither fluorescence quenching nor enhancing effects were found with consistent amounts of homogenate protein. Specific PKA activity was determined as the IP20-inhibitable fraction to account for nonspecific phosphorylation, perhaps due to S6 kinase or a similar enzyme. The basal activity of 38% of total PKA in A6 cells increased by 84% after exposure to vasopressin and by 58% after short exposure to forskolin. In T84 cells exposed to VIP there was a 360% increase over basal activity., Conclusions: These results show that f-Kemptide exhibits acceptable kinetics, and that the assay system can quantitatively and reproducibly measure basal and stimulated PKA activity in cell homogenates.

Recent studies indicate that the actions of arginine vasopressin (AVP) and other agonists that stimulate electrogenic sodium transport in renal epithelial A6 cells are linked to a Ca(2+)-mobilizing signal transduction mechanism that involves generation of inositol trisphosphate. Since diacylglycerol is the other product in this pathway, studies were performed to determine the possible role of PKC in the stimulation of sodium transport. AVP induced a biphasic increase in diacylglycerol generation, characterized by an initial rapid rise and then a sustained elevation, and PKC activation, reflected by phosphorylation of a specific 80 kDa myristoylated alanine-rich PKC substrate (MARCKS). To determine the PKC isoform(s) involved in this process, immunoblot analysis was performed using antisera that recognize both classical PKC isoforms, XPKC-I and XPCK-II, cloned from Xenopus oocytes. The transcripts of both isoforms were expressed in the A6 cell. Since protein recognized by antisera was translocated from cytosol to the particulate fraction after exposure to AVP, one or both isoforms were activated in the A6 cell. Further studies showed that cyclohexyladenosine and insulin, additional agonists of sodium transport in A6 cells, also stimulated phosphorylation of MARCKS. These results argue that Ca(2+)-dependent PKC is involved in the action of AVP, and that of other agonists, which stimulate sodium transport.

Over the past decade, intravenous immune globulin therapy (IVIG) has gained widespread use for a variety of clinical disorders. IVIG treatment is associated with a number of complications, including acute renal failure (ARF). Although the cause of IVIG-associated ARF is unknown, it may be related to the stabilizing agent used in the IVIG preparation. The development and resolution of ARF is typically rapid, but is some cases recovery may be delayed and require renal replacement therapy. In such patients, recurrence of ARF may be avoided by selection of a preparation with a different stabilizing agent. Two cases of IVIG-induced ARF are described, and all reported cases are analyzed to assess the probable mechanism of renal injury.

MARCKS proteins are widely distributed in mammalian cells and subserve an important role as probes in the examination of signal transduction processes because they are specific endogenous phosphoreceptors for activated protein kinase C. Experiments were performed to determine whether MARCKS proteins are present in amphibia and to show their usefulness as substrates for stimulated PKC activation, using cultured renal epithelial cells (A6) derived from Xenopus laevis as an experimental model.

Previous studies showed that insulin stimulation of electrogenic Na+ transport in renal epithelial cells is mediated by a calcium-dependent signal transduction mechanism. The present study was performed to determine whether the insulin-induced increase in intracellular Ca2+ (Cai2+) was mediated by hydrolysis of phosphatidylinositol and release of inositol trisphosphate. Experiments were conducted with cultured A6 cells, derived from Xenopus Laevis, grown on permeable supports. Addition of insulin resulted in 2 to 3 fold increases in inositol trisphosphate and a 50% increase in 1,2 diacylglycerol within 10s, which corresponded to the time-course, previously reported, of insulin stimulated increases in Na+ transport and Cai2+. Further studies showed that aldosterone, previously shown to stimulate an increase in 1,4,5-inositol trisphosphate at onset of the rise in Na+ transport, also increased DAG levels during the initial phase of stimulation of Na+ transport. These studies provide the first evidence that a biological response induced by insulin is mediated by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) which results in two products, inositol trisphosphate which causes the release of Ca2+ from intracellular stores and 1,2 diacylglycerol. In addition this study provides further support for the proposal that a common signal transduction mechanism mediates electrogenic Na+ transport by multiple agonists.

The excised patch clamp configuration provides a unique technique for some types of single channel analyses, but maintenance of stable, long-lasting preparations may be confounded by rundown and/or rapid loss of seal. Studies were performed on the amiloride-sensitive Na+ channel, located on the apical surface of A6 cells, to determine whether the nystatin-induced open cell-attached patch could serve as an alternative configuration. Compared to excised inside-out patches, stable preparations were achieved more readily with the open cell-attached patch (9% vs. 56% of attempts). In both preparations, the current voltage (I-V) relation was linear, current amplitudes were equal at opposite equivalent clamped voltages, and Erev was zero in symmetrical Na+ solutions, indicating similar Na+ activities on the cytosolic and external surfaces of the patch. Moreover, there was no evidence that nystatin altered channel activity in the patch because slope conductance (3-4pS) and Erev (75 mV), when the bath was perfused with a high K:low Na solution (ENa = 80 mV), were nearly equal in both patch configurations. Our results therefore indicate that the nystatin-induced open cell-attached patch can serve as an alternative approach to the excised inside-out patch when experiments require modulation of univalent ions in the cytosol.

Vasopressin is known to activate two types of cell surface receptors; V2, coupled to adenylate cyclase, and V1, linked to a Ca(2+)-dependent transduction system. We investigated whether arginine vasopressin (AVP) stimulation of electrogenic sodium transport in A6 cells, derived from Xenopus laevis, is mediated by activation of either one or both types of AVP-specific receptors. AVP caused a rapid increase in electrogenic sodium transport, reflected by the transepithelial potential difference (VT) and equivalent short circuit current (Ieq) measurements. AVP also rapidly increased intracellular Ca2+ (Ca2+i) and total inositol trisphosphate. The increase in Ieq was dependent on the rise in (Ca2+i), because 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) dose-dependently inhibited the Ieq response. There was no evidence, however, that activation of adenylate cyclase mediated AVP-stimulated Ieq; transport was not inhibited after AVP-induced activation of adenylate cyclase was abolished by 2',5'-dideoxyadenosine or when cAMP-dependent protein kinase (PKA) activity was abolished by the specific PKA inhibitor IP20. Further studies showed that although both forskolin and 8-(4-chlorophenylthio)-cAMP stimulated Ieq, this occurred by mechanisms independent of PKA activation. These results indicate that AVP-stimulated Na+ transport is mediated by a V1 receptor and a Ca(2+)-dependent mechanism.

Studies were performed to determine the primary signal transduction mechanism that mediates adenosine stimulation of electrogenic sodium transport in renal epithelial cells. Experiments were performed on cultured amphibian A6 cells with an adenosine analogue that preferentially binds to the A1 receptor, cyclohexyladenosine (CHA). Sodium transport was assessed by the equivalent short circuit current (Ieq). CHA was found to stimulate Ieq via activation of an A1 receptor because (1) the threshold concentration was 1 nM compared to that of 10 microM for the specific A2 agonist CGS21680, (2) CHA inhibited vasopressin (AVP)-stimulated cAMP production by a pertussis toxin-sensitive mechanism, and (3) the action of CHA was inhibited by the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). CHA increased intracellular Ca2+ ([Ca2+]i) and stimulated phosphoinositide turnover at concentrations that increased Ieq and in a time course that paralleled the increase in Ieq. Ion transport was stimulated by a Ca(2+)-dependent mechanism because the CHA induced increase in Ieq was inhibited by chelating [Ca2+]i with 5,5'dimethyl BAPTA in a dose-dependent manner, with a Ki of approximately 10 microM. The increase in Ieq was also dose-dependently inhibited by the specific PKC inhibitors dihydroxychlorpromazine and chelerythrine, and by trifluoperazine which inhibits PKC and calmodulin. Further studies indicated that CHA-stimulated Ieq was independent of cAMP generation because CHA did not induce an increase in cAMP accumulation parallel to the increase in Ieq in a dose-response analysis, and the adenylate cyclase inhibitor 2',5' dideoxy-adenosine (DDA) did not affect the CHA-induced increase in Ieq.(ABSTRACT TRUNCATED AT 250 WORDS)

This paper is the first in a new Clinical Feature Series that will be a regular feature in future issues of The Yale Journal of Biology and Medicine. Papers in the series will focus on cases and disease processes of general interest to the practicing clinician, with the goal being to present the perspectives of expert clinicians regarding the accurate diagnosis and effective treatment of the diseases being discussed. The following case was presented at Medical Grand Rounds at the Yale-New Haven Hospital and the Yale School of Medicine by John P. Hayslett, Professor of Medicine (Nephrology) with accompanying analysis of pathological specimens by Dr. Hugh Carey, a Postdoctoral Fellow of the Pathology staff. The patient whose case is presented was also present to describe her experience with the illness and the course of treatment.

Objective: To evaluate response to therapy over one year as a predictor of several longterm outcomes in lupus nephritis., Methods: Response to treatment was evaluated by comparing serum creatinine and 24 h urine protein excretion at initial renal biopsy to those obtained after one year of treatment. Response at one year was evaluated as a predictor of renal failure, death due to lupus nephritis, and total lupus mortality, using survival analysis., Results: Eighty-five patients with lupus nephritis diagnosed between 1967 and 1983 and followed through 1990 were studied. Change in proteinuria was a powerful predictor of renal failure (p = 0.001) death due to lupus nephritis (p < 0.001) and overall lupus mortality (p = 0.001). In contrast to a recent study of patients selected for severe lupus nephritis, serum creatinine was not found to be of prognostic significance., Conclusion: Response of proteinuria to treatment over one year is a useful predictor of longterm outcomes in lupus nephritis.

Objective: In a cohort of 87 patients with lupus nephritis, delay between the detection of the onset of renal disease and renal biopsy was a significant predictor at the time of a first renal biopsy for subsequent renal insufficiency (relative risk - 4.9; 95% confidence interval = 1.7 to 14.5; p < 0.001) and death due to lupus renal involvement (relative risk = 6.7; 95% confidence interval = 2.1 to 21.2; p < 0.001). We evaluated the role of lead time bias, 2 variants of prognostic selection bias (length biased sampling), and the benefit of early treatment as explanations for this effect., Methods and Results: Evaluation using the time of renal onset rather than the time of renal biopsy for the analysis suggested that lead time bias was unlikely to be an explanation for the effect of duration on renal insufficiency or death due to renal involvement. Identical values of age, serum creatinine and 24 hour urinary protein excretion at renal onset for those with a long duration versus short duration prior to biopsy, suggested that differences in prognostic selection were unlikely to explain the observed results. A 2nd type of prognostic selection bias arising from the failure to include patients who did not undergo a renal biopsy was further assessed by statistical simulation. The results of this approach indicated that prognostic selection bias was not solely responsible for the significant associations. Because treatment with high dose prednisone and immunosuppressive drugs was not instituted until a renal biopsy had been performed, delay in instituting these therapies remained a possible explanation for the increased frequency of renal insufficiency and death due to renal involvement observed in those with longer delays before renal biopsy. In addition, there was significant deterioration in serum creatinine (median change 0.6 mg/dl) and 24 hour urinary protein excretion (median change 2.5 gm) over the period from renal onset to renal biopsy, and significantly higher scores for the activity, chronicity and tubulointerstitial indices on renal biopsy in those in whom therapy was delayed., Conclusion: Prompt therapy with prednisone and immunosuppressive agents in lupus nephritis has a beneficial effect on longterm prognosis.

Studies were performed to determine the signal transduction mechanism involved in the onset of insulin stimulated electrogenic sodium transport (Ieq) in cultured A6 cells. Insulin stimulated Ieq at a threshold concentration of one nM and a half-maximum concentration of approximately 3 nM. The onset of action occurred within 10 seconds and the increase in Ieq was augmented by pretreatment with aldosterone, similar to the action of vasopressin. Insulin stimulated an increase in Ca2+i in a dose-dependent manner that involved release from intracellular stores. Hormone stimulated Ieq was dependent on increases in Ca2+i because pretreatment with 5, 5' dimethyl BAPTA/AM blocked the increase in sodium transport. Further studies with dihydroxyclorpromazine, trifluoperazine and genistein, inhibitors of PKC, Ca2+i dependent, calmodulin dependent kinases and tyrosine kinase, respectively, suggested that the action of insulin was dependent on activation of these kinases. In contrast, insulin stimulated Ieq was independent of changes in cAMP, because insulin did not increase the accumulation of cAMP, and inhibition of adenylate cyclase with 2', 5' dideoxyadenosine did not affect transport. These results suggest that insulin, as previously shown for aldosterone, activates apical membrane amiloride sensitive sodium channels by a calcium-dependent second messenger system.

Since the metabolic changes in normal pregnancy are diabetogenic, pregnancy imposes a severe stress on the metabolic milieu of diabetic patients. Moreover, many patients with long-standing diabetes have vascular complications, including retinopathy, renal insufficiency, nephrotic syndrome and hypertension, all representing separate risk factors for optimal fetal development. Recent experience has suggested that maternal hyperglycaemia, and associated fetal hyperinsulinaemia, may represent an important factor in the development of fetal complications. During the past two to three decades the incidence of perinatal deaths in all categories of diabetics has been reduced to a level that approaches the rate in healthy gravidas when severe congenital anomalies are excluded. Fetal and neonatal morbidity have also been reduced, although rates of congenital anomalies, hydramnios and respiratory distress syndrome remain high. Although the morbidity associated with oedema formation and hypertension is elevated, with meticulous management of patients with diabetic nephropathy, especially in the absence of severe renal insufficiency and/or severe hypertension, pregnancy performance and outcome can be similar to that of other insulin-dependent diabetic patients.

Objective: To assess the clinical, laboratory, and renal biopsy predictors of long-term outcome in lupus nephritis and to investigate the time-dependence of these predictors., Methods: Eighty-seven lupus nephritis patients were studied retrospectively for the outcomes renal failure and fatality due to renal involvement. In addition to a conventional Cox model analysis, a new generalized time-dependent analytic approach was developed and used to assess the time-dependence of a predictor variable's importance., Results: The mean followup time was 11.9 years. Renal failure (n = 19) was significantly predicted by measures of renal function (abnormal serum creatinine levels, proteinuria, duration of prior renal disease) and immunologic activity (elevated DNA binding, hypocomplementemia, and thrombocytopenia), by overall lupus disease activity measures (le Riche index, Lupus Activity Criteria Count), and by the activity index, the tubulointerstitial index, and the amount of subepithelial deposits on renal biopsy. In general, the laboratory predictors were significantly better prognostic markers in the early years after biopsy, the disease activity measures were best in the later years, and the biopsy variables were significant predictors over the entire observation period. In contrast to the renal failure outcome, the best predictors for death not directly related to lupus nephritis (n = 17) were the extent of comorbid diseases (principally vascular diseases), older age, and the chronicity index. All three predicted well over the extended observation period., Conclusion: The major predictor variables for renal outcomes and nonrenal outcomes are distinct. The time-dependence of the predictive ability of some variables may be important in managing individual patients. The new generalized time-dependent analytic technique may have widespread application in studies to identify prognostic factors for established disease or risk factors for the development of disease.

Of an inception cohort of 87 patients with lupus nephritis who underwent a renal biopsy, 42 underwent second biopsies a median of 25 months later. From first to second biopsy, focal and diffuse proliferative nephritis (World Health Organization classes III and IV) became less frequent, and mesangial hypercellularity (class II) and a membranous pattern (class V) increased. The National Institutes of Health activity index and mesangial and subendothelial deposits declined while the chronicity index, a tubulointerstitial index, and subepithelial deposits increased. The biopsy improvement in urinary protein excretion was best explained by decreases in the activity index score and the amount of subendothelial deposits. A decrease in the amount of subendothelial deposits tended to predict an improvement in the serum creatinine level from first to second biopsy. With follow-up from second biopsy in excess of 7 years, the best predictors of long-term outcome were the ultrastructural variables mesangial, subendothelial and subepithelial deposits. When the change in biopsy predictors from first to second biopsy was evaluated, a decrease in the amount of mesangial or subendothelial deposits was best at predicting a lower risk of renal impairment, renal insufficiency, and mortality. The results confirm the importance of immune complex deposition as measured by electron microscopy in the pathogenesis of lupus nephritis and suggest that control of this process may alter renal function and prognosis.

An inception cohort of 87 patients with lupus nephritis was evaluated using a classification tree regression technique. Four relevant outcomes were studied: (1) renal insufficiency (serum creatinine > 5.0 mg/dl); (2) renal failure; (3) death due to renal involvement; and (4) any death due to systemic lupus erythematosus. All 4 outcomes could be predicted by one or more renal severity measures (serum creatinine, 24-h urinary protein excretion, nephrotic syndrome, or duration of prior renal disease), and among those with nonsevere renal disease, with a single disease activity measure (the National Institutes of Health or le Riche index). In general 3 prognostic groups (high, intermediate and low risk) could be identified for each outcome. Our results demonstrate the value of regression tree techniques in studies of prognosis and are compatible with a hypothesis of the interaction of disease activity with organ damage in lupus nephritis.

This review provides an analysis of reports published since 1980 on the effect of systemic lupus erythematosus (SLE) on pregnancy and pregnancy outcome. The question whether pregnancy increases clinical flares and the severity of flares in patients with SLE during pregnancy has not been resolved because of difficulty in defining exacerbations of SLE and of preeclampsia. An analysis of major detailed reports indicates that maternal complications are reduced in patients who are in clinical remission prior to the onset of pregnancy compared with women with persistent disease activity. Complications are observed in 30%-50% of patients with inactive disease at onset of gestation. After exclusion of spontaneous abortions during the first trimester, fetal survival was 85%-90% in most reported case series. The best outcomes were reported in patients with inactive disease at onset of pregnancy. It seems likely that some maternal complications and fetal wastage in this population are related to anticardiolipin antibodies.

Acute, usually reversible, renal failure has been observed in patients with normal or minimally altered glomeruli on renal biopsy. This review aims to examine the clinical features of acute renal failure in these patients and to evaluate factors that may contribute to the reduction in glomerular filtration rate (GFR). In an analysis of 79 cases affecting 75 patients reported in the English literature since 1966, with acute renal failure associated with minimal change disease or mild histopathological changes in glomeruli, the average age was 58 +/- 2 years (mean +/- 5 SEM), urine protein excretion 11.6 +/- 0.6 g/d, and serum albumin level 19 +/- 1 g/L (1.9 +/- 0.1 g/dL). Acute renal failure was documented an average of 29 +/- 5 days after onset of nephrotic syndrome, and persisted for 7 weeks in 62 episodes in the 58 patients in whom recovery of renal function occurred. Fourteen patients died of uremia or required chronic dialysis, and 3 were lost to follow-up. Although plasma volume depletion was sometimes cited as the cause of renal failure, objective signs of hypovolemia were not documented and most patients did not improve after treatment designed to correct volume deficits. In contrast, histopathological changes consistent with acute tubular necrosis (ATN) were observed in at least 60% of cases. Since the pathogenesis of acute renal failure in minimal change nephrotic syndrome is unknown, we evaluated hemodynamic determinants of GFR in patients with minimal change disease with normal or near-normal renal function, and in relevant animal models, to obtain insights into the effect of nephrotic syndrome on GFR. Although acute renal failure is uncommon, GFR is reduced concurrently with nephrotic syndrome in approximately 30% of children and adults. Absolute and effective blood volume and renal plasma flow are relatively well preserved. However, clinical and experimental observations suggest that the glomerular ultrafiltration coefficient may be reduced by as much as 50%. These findings, together with renal biopsy changes in cases with acute renal failure, suggest that severe reductions in GFR in some patients with minimal change nephrotic syndrome may result from an interaction between acute ischemic tissue injury and preexisting intrinsic renal abnormalities.

Functional adaptation of the remnant intestine after extensive resection of small bowel is well documented. The effects of partial resection of large bowel on the remaining colon have not been characterized. Transepithelial potential (VT), tissue resistance (RT), and short-circuit current (Isc) were measured in vitro across distal colonic tissue of rats three weeks after proximal hemicolectomy with ileotransversotomy and compared to the same parameters measured in the distal colon of control animals. In a second series of experiments, an in vivo perfusion technique was used to measure changes in sodium, potassium, and water transport in distal colon following proximal hemicolectomy. A 2.5-fold increase in VT (P less than 0.01), a 62% increase in RT (P less than 0.001), and a 35% increase in Isc (P less than 0.05) were observed three weeks following hemicolectomy when compared to control animals. A 64% increase in net sodium absorption (P less than 0.025), no significant change in net potassium transport, and a 115% increase in net water absorption (P less than 0.01) were demonstrated in hemicolectomized animals when compared to control. It is concluded that in the rat the distal colon is capable of functional adaptation to increase net sodium and water absorption within three weeks after proximal hemicolectomy. The mechanism responsible for this adaptive process has yet to be defined. Our findings may explain the lack of chronic diarrhea in patients undergoing right hemicolectomy.

Studies were performed on monolayers of cultured A6 cells, grown on permeable filters, to determine the second messenger system involved in the aldosterone-induced increase in electrogenic sodium transport. Addition of aldosterone (1 microM) to the solution bathing the basal surface of cells caused both an increase in Isc and threefold transient rise in intracellular calcium Cai2+ after a delay of approximately 60 min. Because both events were inhibited by actinomycin D and cyclohexamide, they appeared to require transcriptional and translational processes. Addition of BAPTA to the bathing media to chelate Cai2+ reduced Isc and the delayed Cai2+ transient; 50 microM BAPTA inhibited Isc and the rise in Cai2+ by greater than 80%. Further studies suggested that the action of aldosterone to increase Isc may be dependent on a calcium/calmodulin-dependent protein kinase, because W-7 and trifluoperazine reduced the aldosterone-induced Isc in a dose-dependent manner. Taken together, these observations suggest that calcium is a second messenger for the action of aldosterone on sodium transport, and suggest, for the first time, that agonists which bind to intracellular receptors can utilize, via delayed processes dependent on de novo transcription and translation, intracellular second messenger systems to regulate target cell function.

The short-term prognosis of lupus nephritis was evaluated by assessing serum creatinine 12 months after renal biopsy in 87 patients with lupus nephritis. On univariate analysis, significant clinical and laboratory predictors of this outcome included clinical signs of renal injury (serum creatinine, 24-hour urinary protein, prolonged renal disease, nephrotic syndrome, serum albumin), as well as thrombocytopenia, older age, and coexisting illness or hypertension at the time of biopsy. On renal biopsy, diffuse proliferative nephritis, higher activity, chronicity, or tubulointerstitial scores, or subendothelial or subepithelial electron dense deposits predicted a higher serum creatinine 12 months after biopsy. A clinical predictive model was developed which included as independent predictors serum creatinine, age, platelet count and 24-hour urinary protein. Any one of three biopsy variables added information to the clinical prediction model: a marked quantity of subendothelial deposits (p = 0.02), a higher activity index score (p = 0.02), or the presence of diffuse proliferative lupus nephritis (p = 0.05). However, the relative predictive accuracy of the clinical model did not improve with the addition of any of the biopsy variables. The value of renal biopsy in lupus nephritis is discussed based on the ability of biopsy information to confirm the prognosis, to add new predictive information for a group of subjects, and to improve predictive accuracy for individual patients.

Recent studies provide important insights into maternal complications in patients with systemic lupus erythematosus (SLE) established before onset of pregnancy. Exacerbations or relapse occur during the course of pregnancy and immediately postpartum in 25% to 60% of pregnancies. However, the likelihood of increased clinical activity of SLE during pregnancy is influenced by signs of activity present at onset of pregnancy. In the absence of signs of clinical activity for at least 6 months before conception, relapses occur in about one third, whereas in patients with clinical activity at onset of pregnancy, persistent activity or exacerbations occur in approximately two thirds. Fetal survival in these patients parallels the incidence of SLE activity: 85% to 95% in the group with inactive disease at conception and 50% to 80% in subjects with active disease at onset of pregnancy. The introduction of an assay for anticardiolipids has led to a new concept for the pathogenesis of autoimmune disease, namely immune-related thrombosis. Recent studies suggest that this mechanism may play an important role in clinical episodes in SLE, involving late fetal death and maternal arterial and venous thrombosis.

The effect of gestation on the rate of decline in renal function was studied in 11 pregnancies complicated by diabetic nephropathy. For each pregnancy, serum creatinine levels were available within 4 years before pregnancy, during pregnancy, and within 4 years after delivery. Although all of these patients were hypertensive and had increased proteinuria during pregnancy, the mean serum creatinine just prior to conception (1.3 +/- 0.5 mg/dl) and the last follow-up value (1.2 +/- 0.3 mg/dl) were not significantly different. When the inverse of serum creatinine (1/Scr) was used to estimate creatinine clearance, the renal function was either improved or remained stable in the majority of the pregnancies (7 of 11). The observed decline in renal function through the end of follow-up appeared to be consistent with the expected natural course of diabetic nephropathy in the absence of pregnancy. Furthermore, the slope for inverse serum creatinine before and after pregnancy was not significantly different. In conclusion, pregnancy in patients with mild to moderate diabetic nephropathy does not seem to accelerate the rate of decline in renal function.

Chronic potassium loading results in an adaptive change in renal tubular epithelium which increases the capacity for potassium excretion. The present study was performed to evaluate the role of aldosterone in renal potassium adaptation, since hyperaldosteronism stimulates potassium secretion, and potassium loading increases the production of aldosterone. Experiments were performed in animals with intact adrenal glands, and in adrenalectomized animals (Adx) replaced with basal physiologic amounts of corticosterone, which were not replaced with aldosterone, or were chronically infused with aldosterone to achieve either basal plasma levels or elevated levels. Chronic potassium loading in adrenal intact animals was associated with a statistically significant higher rate of urinary potassium excretion (3.57 +/- 0.30 microEq/min/100 g BW) compared to the control rate (2.54 +/- 0.25 microEq/min/100 g BW, p less than 0.05), during acute infusion of KCl. In potassium loaded Adx animals, with selective replacement of adrenal hormones, the maximum rate of potassium excretion was blunted in the absence of aldosterone, compared to potassium loaded animals with intact adrenal glands. In contrast, when Adx animals were infused chronically with aldosterone, to achieve basal or elevated plasma levels, the maximum rate of potassium excretion was not blunted, although at basal aldosterone levels increased potassium excretion was due, at least in part, to hyperkalemia. These results indicate that the induction of renal potassium adaptation after a week or more of chronic potassium loading is dependent on the action of hyperaldosteronism on renal tubular epithelium.

The present study was performed to answer the question: Is the action of aldosterone on electrolyte transport and electrical properties similar in all target tissues? Studies were performed in vivo in control animals and rats with secondary hyperaldosteronism, caused by a sodium-free diet, to compare the effects of hyperaldosteronism on distal colon with hormone-induced changes in proximal colon. In distal colon aldosterone increased net sodium absorption and potassium secretion approximately threefold. Transmural potential difference increased from -15 +/- 2 to -83 +/- 3 mV (lumen negative) and ISC rose from 167 +/- 26 to 1,023 +/- 17 microA X cm-2. These aldosterone-induced responses were completely inhibited by 0.1 mM amiloride. In contrast, in proximal colon potential difference was unchanged or increased slightly in experimental animals and ISC increased only 28% above control, although increases in net sodium and potassium transport were similar to changes observed in distal colon. Amiloride did not reduce sodium absorption in proximal colon of animals with hyperaldosteronism; ISC was decreased by 43%. These studies demonstrate that rat proximal colon is an aldosterone-sensitive tissue, but that the mechanism by which aldosterone influences sodium transport is not identical in distal and proximal portions of colon.