Advanced diabetic nephropathy with nephrotic range proteinuria: a pilot study of the long-term efficacy of subcutaneous ACTH gel on proteinuria, progression of CKD, and urinary levels of VEGF and MCP-1.

BACKGROUND AND OBJECTIVE: Adrenocorticotropic hormone (ACTH) is able to reduce proteinuria in nondiabetic glomerulopathies through activation of melanocortin receptors (MCR) expressed in the podocyte. To determine the efficacy of ACTH, we conducted a randomized, open-label pilot trial of ACTH gel in patients with advanced diabetic nephropathy. STUDY DESIGN: Twenty-three (23) patients with diabetic nephropathy were randomized to daily subcutaneous (SQ) injections of 16 or 32 units of ACTH gel for six months. Outcome. The primary endpoint was the percentage of patients achieving a complete remission (<300 mg/24 hours) within 6 months. Exploratory endpoints included the percentage of partial (50% reduction) remissions, changes in Cr, and urinary cytokine markers. RESULTS: After 6 months of ACTH gel therapy, 8 of 14 (57%) patients achieved a complete (n = 1) or partial (n = 7) remission. In the low-dose ACTH gel group (16 units), urinary protein fell from 6709 + 953 to 2224 + 489 mg/24 hrs (P < 0.001). In contrast, 2 of 6 patients in the 32-unit group achieved partial remission, but aggregate proteinuria (5324 + 751 to 5154 + 853 mg/24 hours) did not change. Urinary VEGF increased from 388 to 1346 pg/mg urinary creatinine (P < 0.02) in the low-dose group but remained unchanged in the high-dose group. CONCLUSION: ACTH gel stabilizes renal function and reduces urinary protein for up to 6 months after treatment. The ClinTrials.gov identifier is NCT01028287.

The role of early and sufficient isolated venovenous ultrafiltration in heart failure patients with pulmonary and systemic congestion.

Hypervolemia, present in at least 70% of patients with decompensated heart failure, results in renal dysfunction due to increased renal venous pressure, impaired renal autoregulation, and decreased renal blood flow that are associated with increased morbidity and mortality. Loop diuretics, widely used in congested patients, result in the production of hypotonic urine and neurohormonal activation. In contrast, ultrafiltration (UF) removes isotonic fluid without increasing renin secretion by the macula densa. Simplified devices that permit us to perform UF with peripheral venous access, adjustable blood flows, and small extracorporeal blood volumes make this therapy feasible at most hospitals and in less acute care settings. Conflicting results on the effects of UF in heart failure patients underscore the challenges of patient selection and choice of fluid removal rates. Unfavorable outcomes in patients undergoing UF in the midst of cardiorenal syndrome type 1 are in contrast with the sustained benefits of UF initiated before unsuccessful use of high-dose intravenous (IV) diuretics. UF rates should be based on a precise knowledge of the degree of hypervolemia and careful assessment of blood volume changes, so that extracellular fluid gradually refills the intravascular space and volume depletion is avoided. Poor outcomes are likely to occur if fluid removal rates are not tailored to individual patients' clinical characteristics. A large trial is ongoing to determine if a strategy of early UF, initiated before renal function is worsened by other therapies, is superior to IV diuretics in reducing 90-day heart-failure-related hospitalizations in patients with pulmonary and systemic congestion.

LJP 394 (abetimus sodium, Riquent) in the management of systemic lupus erythematosus.

LJP 394 (abetimus, Riquent, La Jolla Pharmaceuticals) is four oligonucleotide B cell toleragen which acts as an 'anti-anti DNA'. Given as a weekly infusion, Phase 1, 2, and 3 studies with this biologic on close to 1,000 patients have demonstrated no toxicity of any note. In patients with lupus nephritis and an elevated anti-DNA (Farr assay) who have a high affinity to LJP 394, the drug significantly decreases anti-DNA, improves quality of life, and trends towards reducing renal flares. LJP 394 is a promising induction and/or maintenance therapy for lupus patients with elevated anti-DNA and active disease.

Fenoldopam mesylate blocks reductions in renal plasma flow after radiocontrast dye infusion: a pilot trial in the prevention of contrast nephropathy.

BACKGROUND: Radiocontrast nephropathy (RCN) is a common source of acute renal failure in hospitalized patients and is associated with increased morbidity and mortality rates. Fenoldopam mesylate is a dopamine A1 receptor agonist that augments renal plasma flow (RPF) in patients with normotensive and hypertensive conditions. To determine whether fenoldopam mesylate attenuates reductions in RPF after contrast infusion, we conducted a double-blind, randomized, placebo-controlled pilot trial of fenoldopam mesylate in patients who underwent contrast angiography. METHODS: Fifty-one patients with chronic renal insufficiency (creatinine level, 2.0-5.0 mg/dL) who were undergoing contrast angiography were screened, and 45 patients were randomized to receive normal saline solution (1/2 NS) or 1/2 NS plus fenoldopam mesylate at 0.1 microg/kg/min at lease 1 hour before infusion with contrast dye. Serum creatinine level was measured at baseline and at 24, 48, and 72 hours after angiography. The primary endpoint was change in RPF 1 hour after contrast infusion. The secondary endpoint was incidence of RCN, defined as a 0.5 mg/dL or a 25% rise in serum creatinine level at 48 hours. RESULTS: RPF at 1 hour after angiography was 15.8% above baseline in the fenoldopam mesylate group compared with 33.2% below baseline in the 1/2 NS group (P <.05). The incidence rate of RCN at 48 hours was 41.0% in the 1/2 NS group versus 21% in the fenoldopam mesylate group (P =.148). Among patients with diabetes, the incidence rate of RCN tended to be higher in the 1/2 NS group compared with the fenoldopam mesylate group (64% vs 33%; P =.14). The peak serum creatinine level at 72 hours after contrast infusion was significantly higher at in the 1/2 NS group (creatinine level, 3.6 +/- 1.0 mg/dL) compared with the fenoldopam mesylate group (creatinine level, 2.8 +/- 0.35 mg/dL; P <.05). RPF was significantly (P <.0001) reduced in patients with RCN compared with patients in whom RCN did not develop. CONCLUSION: The results of this pilot trial suggest that fenoldopam mesylate is a promising prophylactic agent for RCN and that larger multicenter trials should be conducted to prove its efficacy.

Design and rationale of CONTRAST--a prospective, randomized, placebo-controlled trial of fenoldopam mesylate for the prevention of radiocontrast nephropathy.

Radiocontrast-induced nephropathy develops in approximately 10% to 20% of patients following administration of iodine-based dye and is one of the most prognostically detrimental complications that invasive cardiologists and radiologists encounter. Preexisting renal dysfunction and diabetes mellitus are two of the most powerful predictors of the likelihood of developing acute renal insufficiency after contrast delivery. To date, only adequate preprocedural hydration and postprocedural hydration to offset dehydration from contrast-induced diuresis have been shown to be effective in preventing this condition. Fenoldopam mesylate, a systemic vasodilator currently FDA-approved for short-term, in-hospital management of severe hypertension, has been shown to increase renal plasma flow in patients with and without chronic renal insufficiency. As a selective agonist of the dopamine-1 receptor, fenoldopam may preserve outer medullary renal blood flow and thereby attenuate radiocontrast-induced nephropathy. Small studies with fenoldopam prior to iodine-based dye administration have demonstrated low rates of radiocontrast nephropathy, and a larger, randomized trial has found that renal blood flow 1 hour after angiography rose in the fenoldopam group compared to a decline in the placebo group. The CONTRAST study has been designed to determine whether fenoldopam is indeed effective in diminishing the occurrence of radiocontrast-induced nephropathy.

Fenoldopam, a dopamine agonist, for hypertensive emergency: a multicenter randomized trial. Fenoldopam Study Group.

UNLABELLED: Despite successful therapies for chronic hypertension, hospital admissions for hypertensive emergency more than tripled between 1983 and 1992. OBJECTIVE: To examine the safety and efficacy of fenoldopam, the first antihypertensive with selective and specific action on vascular dopamine (DA1) receptors, in a clinical trial involving emergency department patients with true hypertensive emergencies. METHODS: Patients with a sustained diastolic blood pressure (DBP) of > or =120 mm Hg and evidence of target organ compromise were randomized in a double-blinded manner to one of four fixed doses of intravenous fenoldopam (0.01, 0.03, 0.1, or 0.3 microg/kg/min) for 24 hours. The primary endpoint was the magnitude of DBP reduction in each of the three higher-dose groups after four hours of fenoldopam treatment compared with the lowest-dose group. RESULTS: One hundred seven participants from 21 centers were enrolled, and 94 patients received fenoldopam. Evidence of acute target-organ damage included new renal dysfunction or hematuria (50%), acute congestive heart failure or myocardial ischemia (48%), and papilledema or grade III-IV hypertensive retinopathy (34%). The DBP decreased in a dose-dependent fashion, with significant differences between the 0.1- and 0.3-microg/kg/min groups compared with the lowest-dose group. Treatment was well tolerated, and there were no deaths or serious adverse events during follow-up, up to 48 hours. All patients were successfully transitioned to oral or transdermal antihypertensives with maintenance of blood pressure control. CONCLUSIONS: Fenoldopam safely and effectively lowers blood pressure in a dose-dependent manner in patients with hypertensive emergencies. Observations supporting potential risk factors for hypertensive emergency are discussed.

Heat shock proteins 70 and 90 increase calcineurin activity in vitro through calmodulin-dependent and independent mechanisms.

We have shown that heat shock proteins (HSPs) associated with steroid receptor complexes are involved in the activation of calcineurin by aldosterone and dexamethasone. To determine whether HSPs directly interact with calcineurin, we measured the effect of HSPs 90, 70 and 56 on calcineurin activity in a cell-free, in vitro system using a calcineurin-specific substrate. HSP-90 (75 or 100 nM) significantly increased calcineurin V(max) in the presence of calmodulin, while maximal stimulation by HSP-70 occurred at 50 nM. Bovine serum albumin (BSA) and actin did not change basal calcineurin activity indicating that HSP-90 and HSP-70 specifically activate calcineurin. Neither HSP-70, HSP-56, nor ATP augmented HSP-90-induced activation of calcineurin. In the absence of calmodulin, HSP-90 restored calcineurin activity to basal levels while higher concentrations (333 and 500 nM) increased calcineurin activity. In contrast, HSP-70 failed to activate calcineurin activity in the absence of calmodulin. Immunoprecipitation of HSP-90 from in vitro mixtures as well as protein extracts from LLCPK-1 cells demonstrates that calcineurin co-precipitates with HSP-90. In summary: (1) HSP-90 and 70 stimulate calcineurin V(max) in vitro; (2) non-specific protein interactions do not activate calcineurin activity; (3) HSP-70 and HSP-56 do not enhance HSP-90-induced activation of calcineurin; (4) HSP-70 and HSP-90 activate calcineurin via a calmodulin-dependent and independent pathways; (5) Calcineurin co-precipitates with HSP-90 from LLCPK-1 cells as well as cell-free in vitro preparations.

Lupus nephritis: novel immunosuppressive modalities and future directions.

Systemic lupus erythematosus (SLE) is a multisystemic disease characterized by alterations in the regulation of both cellular and humoral immune responses. B cell hyperactivity and genetic aberrations lead to formation of compliment-fixing IgG autoantibodies including anti-DNA and anti-nucleosome antibodies. Pathological T cell clones that recognize double-stranded DNA and nucleosomes further drive B cell production of DNA autoantibodies. Deposition of autoantibodies within the skin, kidney, brain, and other organ systems contributes to the pathophysiology and clinical manifestations of SLE. A growing body of experimental evidence indicates that DNA antibodies contribute to the histological changes observed in lupus nephritis. The binding of anti-DNA and other autoantibodies to basement membranes and other cellular structures within the glomerulus results in activation of compliment and recruitment of inflammatory cells into the glomerulus. The use of high-dose steroid hormones and cytotoxic agents have improved patient and renal survival, but are associated with major infection, infertility, osteoporosis, and secondary malignancies. New pharmacological approaches to the treatment of lupus nephritis will include drugs that deplete specific B cell clones involved in the synthesis of nephritogenic autoantibodies as well as the blocking of signal transduction pathways required for antigen-dependent antibody synthesis. Novel clonal-specific approaches to immunosuppression in patients with SLE offer the potential for precise targeting of the disease pathogenesis and for reducing toxic complications of treatment.

Expression and function of calcineurin in the mammalian nephron: physiological roles, receptor signaling, and ion transport.

Protein phosphorylation is central to the regulation of sodium transport and other cellular processes in the nephron. Complex interactions between protein kinases and phosphatases catalyze the reversible phosphorylation of ion transporting proteins on the apical and basolateral surfaces of renal epithelia. Although the role of protein kinases in regulating sodium transport has been extensively studied, the function of phosphatases in the nephron is less well understood. Calcineurin is a serine-threonine phosphatase that was shown to be the target of cyclosporin A (CsA) and FK-506 in lymphocytes. Calcineurin exists in the cytosol as a heterotrimeric protein composed of an alpha-catalytic subunit, beta-regulatory subunit, and calmodulin; its activity depends on calcium and calmodulin. Three isoforms of the alpha-subunit (alpha-1, alpha-2, alpha-3) and two isoforms of the beta-subunit (beta-1 and beta-2) of calcineurin have been identified. In proximal tubules, alpha-1 isoforms are predominant and exceed alpha-2 expression by fourfold. In the CCD, alpha-1 and alpha-2 expression are approximately equal, whereas alpha-2 subunit expression is greatest in medullary thick ascending limbs (mTAL). Alpha-3 was not detected in any nephron segment. Calcineurin phosphatase activity in the proximal tubule is approximately 10-fold higher than in the connecting tubules (CNT), cortical collecting ducts (CCD), or the mTAL. Protein phosphatases 1 and 2a are also expressed in CCD, and only protein phosphatase 1 can be detected in the proximal tubule. Calcineurin influences basal and stimulated Na/ K-ATPase activity in the proximal and distal nephron. In the CCD, CsA or FK-506 decrease Na/K-ATPase activity by 35% and 85%, respectively; Na/K-ATPase activity in mTAL is decreased by 53% and 56%. Activation of membrane receptors, including adrenergic, dopamanergic, and angiotensin I receptors, also regulates Na/K-ATPAse activity through processes that involve calcineurin. Lastly, steroid hormones including glucocorticoids and mineralocorticoids appear to activate calcineurin phosphatase activity. The mechanism is independent of transcription and appears to involve mechanisms involving heat shock proteins associated with the steroid receptor complex.

Aldosterone and dexamethasone stimulate calcineurin activity through a transcription-independent mechanism involving steroid receptor-associated heat shock proteins.

Heat shock proteins (HSP) are components of the steroid receptor complex and are released into the cell cytosol after hormone binding. We tested whether HSPs released from steroid receptors mediate an increase in calcineurin phosphatase activity by steroid hormones. Aldosterone increased calcineurin activity in microdissected rat cortical collecting ducts (CCD) and connecting tubules, but not in proximal tubules, medullary thick ascending limb, or outer medullary collecting ducts. In contrast, 5 microM dexamethasone increased calcineurin activity in both CCD and proximal tubules. Aldosterone increased CCD calcineurin activity after 30 min and this response was blocked by spironolactone, but not by actinomycin D. An antibody recognizing HSP-56 did not change basal calcineurin activity, but completely blocked the stimulation of calcineurin by aldosterone. Rapamycin, an immunosuppressive drug that stabilizes the HSP-steroid receptor complex, also blocked the aldosterone response, whereas HSP-90 or HSP-70 increased calcineurin activity in permeabilized CCD. In summary, (a) aldosterone increases calcineurin activity in CCD through a transcription-independent process; (b) maneuvers inactivating HSP-56 or slowing HSP disassociation from the receptor complex blocks stimulation of calcineurin by steroid hormones; (c) HSP-90 and HSP-70 increase CCD calcineurin activity in the absence of steroid hormone. We conclude that HSPs released from transformed steroid receptors can stimulate calcineurin activity through a transcription-independent pathway.

Case report: delayed hypercalcemia after rhabdomyolysis-induced acute renal failure.

Abnormal calcium metabolism is a common complication of rhabdomyolysis -induced acute renal failure. During the oliguric phase, patients are frequently hypocalcemic. Hyperphosphatemia and skeletal resistance to parathyroid hormone are believed to be possible underlying mechanisms. In addition, there have been reports of hypercalcemia during the diuretic recovery phase after rhabdomyolysis. The pathophysiology of the hypercalcemia observed in the recovery phase is a subject of debate. Several mechanisms have been proposed, including mobilization of calcium from muscle deposits, secondary hyperparathyroidism, and elevated levels of 1,25 dihydroxyvitamin D. The authors report the case of a 30-year-old man admitted for evaluation of marked hypercalcemia (18.3 mg/dL) who was hospitalized 3 weeks earlier for acute renal failure secondary to rhabdomyolysis. Plasma parathyroid hormone and 1,25 dihydroxyvitamin D levels were suppressed during the period of maximal hypercalcemia. A technetium pyrophosphate scan demonstrated extensive deposition of calcium throughout the pelvic and lower extremity muscles. This case of delayed hypercalcemia after rhabdomyolysis supports the hypothesis that mobilization of calcium deposits from soft tissue, including muscle, is central to the pathogenesis of this syndrome.

Expression of calcineurin activity and alpha-subunit isoforms in specific segments of the rat nephron.

Calcineurin activity and alpha-subunit expression were studied in microdissected proximal tubules (S2), medullary thick ascending limbs (MTAL), cortical collecting ducts (CCD), connecting tubules (CNT), and outer medullary collecting ducts (OMCD). We have shown that cyclosporin A (CsA) and FK-506 inhibit sodium-potassium-adenosinetriphosphatase (Na-K-ATPase) activity in CCD, OMCD, and MTAL but did not uncover the mechanism for resistance of proximal tubule segments to these drugs. Because cells expressing high calcineurin activity are relatively resistant to the biological effects of CsA and FK-506, we hypothesized that the resistance of proximal tubules may be linked to increased calcineurin expression. Consequently, we measured calcineurin activity in microdissected tubules using a calcineurin-specific substrate. Calcineurin activity in S2 proximal tubule segments was 10-fold higher than in CCD, CNT, OMCD, or MTAL. FK-506 (6.0 ng/ml) inhibited calcineurin activity in CCD, CNT, and MTAL but not S2; 250 ng/ml FK-506 inhibited S2 calcineurin activity by 50%. Likewise, high concentrations of CsA (25 micrograms/ml) and FK-506 (250 ng/ml) inhibited S2 Na-K-ATPase activity by 77 and 73%, respectively. To investigate whether the resistance of S2 segments might be due to differential expression of calcineurin alpha-subunit isoforms, we determined the isoform expression by Western blot analysis using isoform-specific antibodies against the alpha 1-, alpha 2-, and alpha 3-isoforms. We found that alpha 1 expression in S2 was significantly greater than in the CCD and MTAL, whereas alpha 2 expression in the S2 was significantly less than in CCD and MTAL. No alpha 3 was detected in any nephron segment tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium-dependent net urea transport in rat initial inner medullary collecting ducts.

We reported that feeding rats 8% protein for 3 wk induces net urea transport and morphologic changes in initial inner medullary collecting ducts (IMCDs) which are not present in rats fed 18% protein. In this study, we measured net urea transport in microperfused initial IMCDs from rats fed 8% protein for > or = 3 wk and tested the effect of inhibiting Na+/K(+)-ATPase activity and found that adding 1 mM ouabain to the bath reversibly inhibited net urea transport from 14 +/- 3 to 6 +/- 2 pmol/mm per min (P < 0.01), and that replacing potassium (with sodium) in the bath reversibly inhibited net urea transport from 18 +/- 3 to 5 +/- 0 pmol/mm per min (P < 0.01). Replacing perfusate sodium with N-methyl-D-glucamine reversibly inhibited net urea transport from 12 +/- 2 to 0 +/- 1 pmol/mm per min (P < 0.01), whereas replacing bath sodium had no significant effect on net urea transport. Adding 10 nM vasopressin to the bath exerted no significant effect on net urea transport. Finally, we measured Na+/K(+)-ATPase activity in initial and terminal IMCDs from rats fed 18% or 8% protein and found no significant difference in either subsegment. Thus, net urea transport in initial IMCDs from rats fed 8% protein for > or = 3 wk requires sodium in the lumen, is reduced by inhibiting Na+/K(+)-ATPase, and is unchanged by vasopressin or phloretin. These results suggest that net urea transport may occur via a novel, secondary active, sodium-urea cotransporter.

Evidence that the inhibition of Na+/K(+)-ATPase activity by FK506 involves calcineurin.

We reported that cyclosporin A (CsA) inhibits Na+/K(+)-ATPase activity in specific segments of the rat nephron. In this study, we tested the hypothesis that cyclosporin A reduces Na+/K(+)-ATPase activity through inhibition of calcineurin. In T cells, cyclosporin A and FK506 bind to immunophilins and inhibit the phosphatase activity of calcineurin; Rapamycin and SDZ 220-384 also bind to immunophilins but do not change calcineurin activity. Na+/K(+)-ATPase activity was measured in microdissected rat proximal tubule (S2 subsegment), medullary thick ascending limb (mTAL), and cortical collecting duct (CCD). First we found that two inhibitors of calcineurin, pentafluorophenol (PFP, 100 mM) and peptide 412 (1 mM), significantly reduced Na+/K(+)-ATPase activity in the CCD by 78% and 70%, respectively. In CCDs, FK506 inhibited Na+/K(+)-ATPase activity by 61 to 85% at concentrations of 1.5 to 6 ng/ml, but not at 0.5 ng/ml. FK506 (6 ng/ml) inhibited Na+/K(+)-ATPase activity in mTALs by 56% but did not inhibit it in S2s or glomeruli. In contrast, Rapamycin (12.5 ng/ml) did not change Na+/K(+)-ATPase activity in CCDs or mTALs, but at a concentration of 12.5 micrograms/ml did block the inhibitory effect of FK506 (6 ng/ml) in both segments. SDZ 220-384 (600 ng/ml) did not change Na+/K(+)-ATPase activity in CCDs. Thus, in CCDs and mTALs: (1) FK506, like cyclosporin A, inhibits Na+/K(+)-ATPase activity; (2) Rapamycin and SDZ 220-384 do not inhibit Na+/K(+)-ATPase activity; and (3) Rapamycin prevents FK506-induced inhibition of Na+/K(+)-ATPase activity. These responses may be explained by a direct inhibition of calcineurin activity yielding lower Na+/K(+)-ATPase activity in CCDs and mTALs.

Expression of Na-K-ATPase alpha- and beta-subunit mRNA and protein isoforms in the rat nephron.

Na-K-ATPase is a heterodimeric complex composed of an alpha-catalytic and a glycosylated beta-subunit. Previous studies using in situ hybridization and Northern blot analysis to determine alpha- and beta-subunit mRNA isoform expression in the rat kidney have given conflicting results. This heterogeneity may be due to detection of alpha 2- or alpha 3-isoforms arising from nonrenal epithelial sources such as peripheral nerves or vascular smooth muscle. To address this possibility, we investigated alpha-subunit mRNA isoform expression in different nephron segments using tubule microdissection and reverse transcription-polymerase chain reaction amplification. Southern blot analysis of polymerase chain reaction products using isoform-specific primers and probes detected the expression of alpha 1- and alpha 3-mRNA isoforms in whole kidney, cortical collecting ducts (CCD), and proximal tubule S2 subsegments (S2). No evidence for alpha 2 was found in kidney or microdissected CCD or S2. To determine whether alpha 1- or alpha 3-mRNA in the CCD or S2 is translated into protein, Western blot analysis of total protein from microdissected S2, CCD, medullary thick ascending limb (MTAL), or outer medullary collecting duct outer stripe (OMCDos) was performed. Total protein was separated according to size by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, then probed using polyclonal antibodies specific for the alpha 1-, alpha 2-, alpha 3-, beta 1-, and beta 2-protein isoforms. Rat brain was used as a positive control and demonstrated that the antibodies could detect a single 97- and 35-kDa band for the alpha- and beta-isoforms, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Nephron segment-specific inhibition of Na+/K(+)-ATPase activity by cyclosporin A.

Decreased kaliuresis and hyperkalemia are common complications of cyclosporin A (CsA) therapy. If CsA significantly inhibits renal tubular Na+/K(+)-ATPase activity, the alteration in transepithelial K+ secretion and K+ homeostasis could result in hyperkalemia. To investigate this possibility, we tested the effects of CsA on Na+/K(+)-ATPase activity in microdissected rat tubules. CsA, at a "toxic" concentration of 600 ng/ml, significantly inhibited Na+/K(+)-ATPase in cortical collecting ducts (CCD), medullary thick ascending limbs (mTAL), and outer medullary collecting ducts from the outer stripe (OMCDos) by 35%, 53%, and 39%, respectively. Cremophore, the commercial vehicle for CsA, did not change Na+/K(+)-ATPase activity in any nephron segment tested. To determine whether CsA inhibits Na+/K(+)-ATPase activity in a dose-dependent manner, microdissected CCD's were incubated with 300, 600, and 2500 ng/ml of CsA for 30 minutes. Na+/K(+)-ATPase activity was inhibited at 600 and 2500 mg/ml, but not at 300 ng/ml. No further inhibition of enzyme activity was noted at 2500 ng/ml. CsA did not change Na+/K(+)-ATPase activity in proximal tubule S1, S2, and S3 subsegments; cortical thick ascending limbs (cTAL), connecting tubules (CNT), or outer medullary collecting ducts from the inner stripe (OMCDis). Prolonging the incubation of CsA with S2 subsegments to 60 minutes did not result in inhibition of Na+/K(+)-ATPase activity. Ouabain-insensitive ATPase activity was unaffected by CsA or its vehicle in any nephron segment tested. In summary, CsA specifically inhibits Na+/K(+)-ATPase activity in the CCD, mTAL, and OMCDos.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemolytic-uremic syndrome following "crack" cocaine inhalation.

The authors present a patient who experienced cocaine-related thrombotic microangiopathy and patchy renal cortical necrosis, associated with the clinical syndrome of microangiopathic hemolytic anemia, thrombocytopenia and acute renal failure, characteristics of the Hemolytic-Uremic syndrome. The proposed pathogenetic mechanisms include: (1) cocaine-induced vasoconstriction and endothelial damage and (2) procoagulant effects of cocaine.