Vitamin D reduces renal NaPi-2 in PTH-infused rats: complexity of vitamin D action on renal P(i) handling.

Acute administration of dihydroxycholecalciferol [1,25(OH)(2)D(3)] blunts phosphaturia and increases urinary cAMP excretion in parathyroid hormone (PTH)-infused parathyroidectomized (PTX) rats. Because chronic administration of 1,25(OH)(2)D(3) enhances the phosphaturic response to exogenous parathyroid hormone despite blunting of urinary cAMP excretion, we have examined the expression of the renal cortex type II Na-P(i) cotransporter (NaPi-2) mRNA and protein in 1) chronic PTX Sabra rats, 2) PTX rats receiving a physiological dose of 1,25(OH)-2-D(3), 3) PTX rats receiving 35 ng/h of PTH, and 4) rats receiving both PTH and 1,25(OH)(2)D(3), for 7 days via osmotic minipumps. Our results confirm that there is increased phosphaturia in the PTH+1,25(OH)(2)D(3)-infused animals despite blunting of urinary cAMP excretion, a reduced filtered load of phosphate, and lack of a phosphaturic effect by 1,25(OH)(2)D(3) alone. Both PTH and 1,25(OH)(2)D(3) significantly reduced expression of renal cortex NaPi-2 mRNA and NaPi-2 protein, and the administration of PTH together with 1,25(OH)(2)D(3) had additive effects in further decreasing NaPi-2 mRNA and NaPi-2 protein levels. Expression of two other epithelial transporters, type 1 Na-sulfate and type 1 Na-glucose cotransporters, were not different between the groups, suggesting specificity of the effects of PTH and 1,25(OH)(2)D(3) on phosphate transport. The effect of chronic administration of 1,25(OH)(2)D(3) has not been noted previously, and the cellular mechanisms and signaling processes that mediate the decrease in NaPi-2 remain to be determined.

Detection of human herpesvirus-8 DNA in kidney allografts prior to the development of Kaposi's sarcoma.

Human herpesvirus-8 (HHV-8) DNA was identified in kidney allografts in 2 of 3 transplant recipients prior to the development of Kaposi's sarcoma, and increase in viral antibody titer was found in the third. Combined genotypic and serologic analyses could be used to identify patients at risk and suggest that the kidney may be a site of HHV-8 latency.

Response to growth hormone therapy in experimental ischemic acute renal failure.

In acute renal failure (ARF), the gene and peptide expression of insulin-like growth factor-I (IGF-I) falls. Because IGF-I is regulated by growth hormone (GH) and because kidney GH receptor expression is also attenuated in ARF, the impaired IGF-I expression may partly reflect local GH resistance. Because IGF-I treatment accelerates recovery from ARF, we determined whether high-dose GH therapy could overcome this putative GH resistance, stimulate IGF-I production, and enhance recovery. Rats with ARF were given 2.5 mg GH or vehicle (V) over 2 days, beginning 24 hours before the onset of ARF. GH prevented weight loss but did not modify the course of ARF. Next we determined whether the failure of GH to modify kidney recovery could reflect a failure to stimulate renal IGF-I gene expression. Rats were treated with GH or V over an 18-hour period beginning 1 day after the induction of ARF. Hepatic IGF-I mRNA and serum IGF-I peptide levels rose significantly with GH treatment, but the low kidney IGF-I mRNA levels did not respond. We conclude that the failure of GH to enhance recovery from ARF is caused by impaired GH-stimulated renal IGF-I production, while the maintenance of body weight likely reflects the systemic effects of the increase in hepatic IGF-I production.

The insulin-like growth factor-I axis in acute renal failure.

We have examined the response of the renal insulin-like growth factor (IGF-I) axis to acute ischemic injury in the rat Key findings included a decrease in IGF-I mRNA and peptide levels, a decrease in GH receptor gene plus protein expression and a decrease in the IGF binding proteins except for IGF binding protein I. Administration of GH to compensate for the reduced GH receptor binding corrected the IGF-I mRNA levels suggesting a relative GH deficiency. Interestingly, IGF-I receptor mRNA levels were unchanged while plasma membrane IGF-I receptor number increased two fold. This appeared to be due to a redistribution of receptors to a membrane location. IGF-I receptor autophosphorylation and tyrosine kinase activity were intact despite severe uremia for up to 6 days. We propose that this increase of functional IGF-I receptors following acute tubular necrosis will sensitize the kidney to the administration of exogenous IGF-I.

Insulin-like growth factor-I treatment to enhance renal function in advanced chronic renal failure.

Because of the potential for IGF-I to enhance renal function in advanced chronic renal failure (CRF) we set out to determine whether IGF-I can induce a sustained increase in renal function in patients with near end-stage renal failure. To this end we first examined the impact of CRF on the pharmacokinetics of IGF-I and then we examined the effect of prolonged IGF-I treatment on the renal function of patients with an average GFR of 17 mL/min/1.73 m2. Interestingly the metabolic clearance rate of IGF-I in CRF subjects was similar to that in normal subjects even though the total serum IGF-I levels rose to higher maximum levels. This increase was due to a reduced volume of IGF-I distribution, a consequence of the elevated serum IGF binding proteins in CRF subjects. Treatment with IGF-I (60 mg/kg twice daily sc) for 31 days resulted in a 14% and 18% increase in the inulin and PAH clearances respectively (n = 6 patients). These parameters returned to basal levels on stopping treatment. Serum immunoreactive IGFBP-3 levels fell and IGFBP-2 and -3 levels rose during IGF-I therapy. Adverse effects were mild, of short duration and easily manageable. Thus IGF-I pharmacokinetics are largely unchanged in CRF and the administration of IGF-I produces a modest improvement in the GFR. These results appear to justify more extensive examination of the therapeutic role of IGF-I in the treatment of CRF.

End-stage renal interstitial fibrosis in an adult ten years after ifosfamide therapy.

A 33-year-old male presented with end-stage renal failure. Renal biopsy showed severe interstitial fibrosis without glomerulopathy or vasculopathy. More than 10 years previously the patient had been successfully treated for recurrent rhabdomyosarcoma. The treatment included ifosfamide, a drug known to cause acute tubular dysfunction. Though a possible synergistic effect of previous radiation which was well within accepted tolerance limits cannot be excluded, it would appear that ifosfamide was almost certainly the major cause of the late onset chronic renal disease.

Clustering of Pneumocystis carinii pneumonia in patients undergoing renal transplantation from living unrelated donors in Iraq and India.

Over the past few years, we have observed a substantial increase in the number of patients followed at our hospital who have undergone renal transplantation from living unrelated donors (LURD). These transplants were all performed in one of two centers: Bagdad, Iraq or Bombay, India. We have observed a parallel increase in the number of cases of Pneumocystis carinii pneumonia (PCP) post-renal transplant. We conducted a ten-year retrospective analysis (1986-1995) of patients who developed PCP post-renal transplant to determine the risk factors associated with the development of this infection, with particular reference to the type of transplant and the center in which the transplant was performed. Over this period, 270 renal transplant patients were followed at this hospital and 10 episodes of PCP were documented (3.7%). Six of these cases occurred within the last 2 years, as compared to only 4 cases in the preceding 8 years. All of the cases observed in the last 2 years occurred in patients who had undergone renal transplantation from LURD in Iraq or in India. During the same period, we observed no cases of PCP in patients who had undergone transplantation in Israel (cadaver or related living donor transplants). We could find no difference between patients undergoing transplant from LURD and those undergoing other transplants in terms of immuno-suppressive therapy, frequency of organ rejection episodes or coexistent CMV infection. All patients were of Arab descent and live in the West Bank. Although we cannot identify any obvious explanation for this association, we believe that these cases represent a true cluster phenomenon. We therefore feel it is warranted for all recipients of renal transplants from living unrelated donors seen in our hospital to receive prophylactic therapy for Pneumocystis carinii pneumonia.

Effect of human recombinant erythropoietin therapy on panel reactive antibodies in chronic dialysis patients.

To examine whether recombinant human erythropoietin (rhEPO) therapy results in decreased presensitization to foreign HLA antigens, we retrospectively analyzed data from 64 of 200 patients treated in a university hospital dialysis center between 1985 and 1995 who had undergone routine panel reactive antibody (PRA%) screening. Though a significant decrease in the annual frequency of highly sensitized patients over the years was noted, 16 patients followed for 27.1 +/- 3.7 months after initiation of rhEPO therapy until transplantation or blood transfusion showed no significant overall decrease in PRA%. Six highly presensitized patients had moderate but significant overall decrease in PRA%. However, in three of these patients the PRA% was unchanged and in the other three patients the PRA% remained over 50%. Thus rhEPO therapy reduced the incidence of highly presensitized patients, but previously presensitized patients remained presensitized. We conclude that removal of transfusional stimulation of lymphocytotoxic antibody production does not appear to benefit previously presensitized patients, possibly due to the maintenance of B-lymphocyte clonal expansion by unknown factors, or even by rhEPO itself.

Successful renal transplantation from two donors with methanol intoxication.

Two patients with acute methanol intoxication are reported, one with acute renal failure. Both were declared brain-dead and kidneys were harvested at 80 and 130 hr after hospital admission. All four kidneys were transplanted and subsequently functioned well. In both donors who had received ethanol treatment, thrombocytopenia was present. The reluctance to use kidneys from such donors and from donors with acute renal failure before harvesting is discussed. Waiting lists for renal transplantation are growing and there is a world-wide shortage of cadaver organs. We were recently surprised to find reluctance to consider two local patients dying from methanol intoxication as suitable organ donors, and we report the outcome of four kidneys transplanted from these donors. We were unable to find any similar cases reported in the English literature.

Carnitine palmitoyltransferase deficiency: an underdiagnosed condition?

Two apparently healthy adults were admitted because of acute muscle cramps, severe weakness, and red urine excretion. Patient No. 1 developed the symptoms following intense exercise and patient No. 2 during a febrile infection. Both of them experienced such episodes in the past, but these were medically misinterpreted. Their present manifestations were accompanied by renal failure which subsided gradually and was found to be a result of rhabdomyolsis and myoglobinuria. Further investigations yielded a deficiency of carnitine palmitoyltransferase as a background to the acute muscular destruction. Examination of a sister of patient No. 2 who had a similar past history revealed the same metabolic disorder. Carnitine palmitoyltransferase deficiency, as a cause of nontraumatic rhabdomyolysis, is a distinct entity in the pathogenesis of acute renal failure. Our experience (3 patients within 2 years) makes us presume that this condition is not as rare as hitherto reported and should rather be considered in cases of 'nonhematuric' red urine and acute renal failure.

22-Oxacalcitriol does not interfere with parathyroid hormone-induced phosphaturia or cyclic-AMP excretion.

The vitamin D analogue, 22-oxacalcitriol [22-oxa-1,25(OH)2 vitamin D3], has pleiotropic effects similar to or greater than calcitriol but has markedly fewer calcemic and phosphatemic effects. To test the hypothesis that the lesser phosphatemic effect of 22-oxacalcitriol is due, at least in part, to a lack of interference with the phosphaturic effect of parathyroid hormone, acute clearance experiments were performed in parathyroidectomized rats receiving continuous 1-34 parathyroid hormone (PTH) infusion together with 22-oxacalcitriol (200 pmol.100 g body weight-1.min-1) or vehicle. In contrast to the previously reported inhibitory effect of calcitriol on PTH-induced phosphaturia, fractional excretion of phosphorus increased similarly in both groups, from 0.05 +/- 0.01 to 0.26 +/- 0.02 (p < 0.01) in the vehicle-infused animals and from 0.04 +/- 0.01 to 0.24 +/- 0.02 (p < 0.01) in the 22-oxacalcitriol-treated rats (p between groups not significant [n.s.]). Urinary cyclic AMP excretion also increased similarly, from 45.5 +/- 5.2 to 101.6 +/- 21.6 (p < 0.01) and from 45.4 +/- 5.6 to 102.6 +/- 16.7 pmol/min (p < 0.01), respectively (p between groups n.s.). In search for a nongenomic mechanism that might account for the disparate effects of 22-oxacalcitriol and calcitriol, OK cells, which are reminiscent of the mammalian proximal tubule cell, were stimulated with calcitriol and 22-oxacalcitriol and free intracellular calcium concentration was determined. At high concentrations, calcitriol caused a dose-dependent increase in [Ca2+]i; 22-oxacalcitriol had no effect on [Ca2+]i at any concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

cGMP antagonizes angiotensin-mediated phosphatidylcholine hydrolysis and C kinase activation in mesangial cells.

Previous studies from this laboratory have shown that in cultured rat mesangial cells (MC), angiotensin II (ANG II) mediates its effects via activation of phosphatidylinositol-specific phospholipase C (PI-PLC) and phosphatidylcholine-specific phospholipase C (PC-PLC) and phospholipase D (PC-PLD). In addition, guanosine 3',5'-cyclic monophosphate (cGMP)-elevating maneuvers that stimulate particulate and soluble guanylate cyclase [atrial natriuretic factor (ANF) and sodium nitroprusside (SNP), respectively] antagonize ANG II-mediated PI-PLC activation. The current study explored whether cGMP impairs ANG II-mediated PC-PLC and PLD activity. The ANG II-stimulated release of the water-soluble metabolites of PC breakdown (phosphorylcholine and choline) was blocked by ANF and SNP. ANG II-stimulated phosphatidic acid and phosphatidylethanol formation were significantly reduced by ANF and SNP, confirming that cGMP blunted PLD activity. The inhibitory effect of cGMP on PLD could be reversed by N-(2-[methylamino]ethyl)-5-isoquinolinesulfonamide, a blocker of cGMP-dependent protein kinase. In parallel experiments, ANF and SNP abrogated sustained diacylglycerol (DAG) accumulation derived from ANG II stimulation of PC hydrolysis, confirming that cGMP diminished PC-PLC activity. Inhibition of PC-derived DAG accumulation by cGMP was associated with a concomitant decrement in ANG II-mediated translocation of protein kinase C (PKC) activity from the cytosol to the membrane. In summary, in MC, cGMP antagonizes ANG II-mediated PC hydrolysis, DAG formation, and PKC activation. We propose that cGMP-mediated inhibition of phospholipid metabolism and PKC translocation plays an important role in MC vasorelaxation.

Angiotensin-mediated phosphatidylcholine hydrolysis and protein kinase C activation in mesangial cells.

Angiotensin II (ANG II) in mesangial cells (MC) promotes phosphatidylinositol (PI) hydrolysis resulting in diacylglycerol (DAG)-mediated increases in protein kinase C (PKC) activity. The paucity of MC inositol lipid prompted us to consider whether phosphatidylcholine (PC) could sustain DAG formation. ANG II released choline and increased phosphatidylethanol (PEt) via PC-phospholipase D (PC-PLD). ANG II also stimulated phosphorylcholine consequent to PC-phospholipase C (PC-PLC) activation. ANG II-mediated PC hydrolysis augmented DAG for 30 min. PC breakdown was influenced by extracellular Ca2+, because Ni2+ partially inhibited ANG II-induced PEt and obliterated agonist-mediated DAG formation. The consequence of Ca2+ modulation of PC metabolism was investigated by measuring PKC activity. Ni2+ had no effect on early (PI-associated) activation by ANG II at 90 s but obviated translocation from cytosol to the membrane at 10 min. The pathway responsible for PC-associated DAG was studied in PKC downregulated cells. Whereas downregulation prevented PLD-mediated PEt elevation, ANG II-stimulated DAG formation in myristate-labeled cells was unaltered, indicating PC-PLC activation. In summary, ANG II stimulates PC-PLD and PC-PLC in MC. PC-PLD is tightly regulated by PKC, whereas PC-PLC is stringently controlled by extracellular Ca2+. ANG II mediated PC breakdown principally via PC-PLC provides a mechanism for maintaining elevated DAG levels and PKC activation.

Endothelin activation of phospholipase D: dual modulation by protein kinase C and Ca2+.

Previous work from this laboratory has identified an endothelin (ET) type A (ETA) receptor on cultured rat renal medullary interstitial cells (RMIC), coupled to phosphatidylinositol-specific phospholipase C (PI-PLC), dihydropyridine-insensitive receptor-operated Ca2+ channels, and phospholipase A2. The current studies explored a role for ET stimulation of phosphatidylcholine-specific phospholipase D (PC-PLD) in intracellular signaling of this cell type. ET stimulated PLD activation, as measured by phosphatidic acid (PA) or phosphatidylethanol (PEt) accumulation, in a time- and concentration-dependent manner. Inhibition of diacylglycerol (DAG) kinase by ethylene glycol dioctanoate or 6-(2)4-[(4-fluorophenyl)-phenylmethylene]-1-piperadinyl]ethy l-7-methyl-5H - thiaxolo-[3,2-alpyrimidin]-5-one (R 59022) failed to blunt PA accumulation, indicating that PLD, and not DAG, was the source of PA. Inhibition of PA phosphohydrolase (PAP) by propranolol increased late accumulation of PA, suggesting that the prevailing metabolic flow was in the direction of PA to DAG. Phorbol 12-myristate 13-acetate (PMA) augmented ET-evoked PEt accumulation, whereas downregulation of protein kinase C (PKC) obviated agonist-induced PEt production. PMA augmentation of PLD activity proceeded independent of cytosolic free Ca2+ concentration. Ca2+ derived from either intracellular or extracellular sources enhanced ET-related PEt accumulation but was without effect in PKC-downregulated cells. Collectively, these observations indicate that ET stimulates PLD production in RMIC. PKC is the major regulator of this process, with Ca2+ playing a secondary, modulatory role. In addition, these data suggest that PC-PLD is coupled to the ETA receptor.

Kidney transplantation in Jerusalem, 1972-89. Kidney Transplant Group.

The results of a small transplant program over 18 years are presented. Two hundred and fifty-six transplantations including 36 living donor transplants were performed in 203 patients. Graft survival at 1, 3, 5 and 10 years without and with cyclosporin A treatment was 57%, 49%, 44%, 38%, and 71%, 69%, 58%, -% (respectively). Patient survival was 83%, 67%, 62%, 54%, and 92%, 90%, 68%, -% (respectively). Recent results with cyclosporin A treatment have shown further improvement. Analysis using the COX model shows that age under 30 years, lack of systemic disease, and the use of cyclosporin A and living donors all improved patient survival. More than 10- and 5-year survival was achieved in 78 and 103 patients, respectively, of whom 53 and 81 have good graft function. Local transplant policy and patient material are discussed.

The in vivo and in vitro effect of calmodulin antagonists on the renal actions of 25(OH) vitamin D3 in the rat.

Previous work from this laboratory has demonstrated that 25(OH) vitamin D3 [25(OH)D3] acutely suppresses the phosphaturic action of parathyroid hormone (PTH) and interferes with the PTH-induced activation of adenylate cyclase (AC). Calmodulin inhibitors block vitamin D-induced Ca2+ transport in the gut and phosphorus uptake in renal BBMV's. We have examined whether calmodulin antagonists affect the renal action of 25(OH)D3. Acute clearance experiments were performed in PTH-infused parathyroidectomized rats receiving 25(OH)D3 after pretreatment with trifluoperazine (TFP) or promethazine (P). In vitro PTH-induced activation of renal AC was also studied in membrane preparations from pretreated rats in the presence of 25(OH)D3. 25(OH)D3 reduced the PTH-stimulated increase in fractional excretion of phosphorus (CP/CIn) from 0.292 +/- 0.024 to 0.195 +/- 0.018 (p less than 0.005) and urinary cAMP from 149.3 +/- 20.3 to 78.1 +/- 10.4 pmol/min (p less than 0.01) and also blunted AC activation in vitro. TFP but not P abolished the effects of 25(OH)D3 both in vivo and in vitro. R 24571 also abolished the in vitro effect of 25(OH)D3. Thus, (1) TFP abolishes both the antiphosphaturic and the AC/cAMP-related actions of 25(OH)D3, (2) P does not have these effects, and (3) R 24571 abolishes the in vitro effect of 25(OH)D3. These results suggest that the antiphosphaturic effect of 25(OH)D3 acting via the AC/cAMP system may be calmodulin dependent.

Renal transplantation is not contraindicated in asymptomatic carriers of hepatitis B surface antigen.

Recent reports showing that the presence of positive tests for hepatitis B surface antigen (HBsAg) is associated with prohibitively high morbidity and mortality suggest that such patients should not be considered for kidney transplantation. The clinical outcome and serology including hepatitis B DNA assays of 11 patients who were HBsAg-positive at the time of transplantation, as well as the hepatic complications in all 200 kidney transplantations during the same period, were analyzed. In the 11 HBsAg-positive patients, no clinical or laboratory evidence suggesting deterioration in liver function over a mean follow-up period of 8.0 +/- 1.7 years was found. Of six patients with fatal or severe chronic liver disease, only one was HBsAg-positive at the time of transplantation and showed no deterioration over 9 years. Two immunosuppressed patients developed anti-HBs antibodies after acute hepatitis B infection. A review of the literature leads to the conclusion that previous reports of poor patient prognosis may represent patients who first showed HBsAg positivity after transplantation or who had preexisting HBsAg-related liver disease. The present findings suggest that asymptomatic patients with positive tests for HBsAg should not be excluded from kidney transplantation programs.