Genotype/phenotype observations in African Americans with Bartter syndrome.

BACKGROUND: Two Bartter syndrome phenotypes have been described, and molecular analyses demonstrate mutations in 1 of 3 genes encoding ascending limb of Henle transporters. We report phenotypic observations in 5 African American children with Bartter syndrome in the context of a distinct genotype. METHODS: Mutation analyses were performed in 5 unrelated African American children with Bartter syndrome. These results were correlated to clinical and laboratory data. Calcium metabolism was evaluated with a bone disk bioassay. RESULTS: Mutation analyses demonstrated homozygous deletion of the ClC-Kb gene in all children. Two children had polyhydramnios and premature birth; the others were born at term and presented with failure to thrive or dehydration. All receive indomethacin, spironolactone, and potassium chloride with improved but borderline hypokalemia. Growth has improved with therapy, but height SD scores range from -3.9- to -1.4. Urinary calcium excretion is normal, and bone disk bioassay shows no abnormal calciotropic activity. No patient had nephrocalcinosis, but renal sonograms show loss of corticomedullary differentiation. CONCLUSIONS: African Americans with Bartter syndrome genotyped to date have homozygous deletion of ClC-Kb Clinical observations in our patients include partial correction of hypokalemia and suboptimal growth despite therapy. Abnormal calciotropic activity and nephrocalcinosis are not seen, but renal ultrasounds are abnormal.

Circulating mediators of proteinuria in idiopathic minimal lesion nephrotic syndrome.

The pathogenesis of proteinuria in idiopathic minimal lesion nephrotic syndrome (IMLNS) remains to be elucidated. The most-accepted hypothesis is that the increased glomerular permeability to plasma proteins results from the effect of circulating factors on glomerular capillaries. This report critically reviews the current studies that have attempted to isolate and characterize this putative factor(s). Products released from hepatocyte or peripheral blood mononuclear cells or isolated by chromatography from serum or plasma have been tested in rats for their role in inducing proteinuria. These factors have been infused into the isolated kidney preparation or into the intact animal as a single venous injection, or continuously by pump for a period of 4 h to 7 days. Several of these isolated factors have been shown to induce proteinuria in rats. However, their exclusive pathogenetic role is questionable since none is always present in all IMLNS patients during relapse. Therefore, the increase in proteinuria in these patients may result from a single or a variety of factors as yet to be identified.

Interleukin-8 alters glomerular heparan sulfate glycosaminoglycan chain size and charge in rats.

We have previously shown that the in vivo infusion of interleukin-8 (IL8) in rats causes albuminuria and an increased catabolism of the heparan sulfate (HS) glycosaminoglycans (GAG). The purpose of this study was to characterize further the in vivo effect of IL8 on rat HSGAG. The left renal artery of male rats was continuously infused with IL8 (750 ng/ml, 4 rats) or 1% bovine serum albumin (3 rats) using an osmotic pump. On the 5th day of infusion, 35sulfate (1.0 mCi/100 g) was given intraperitoneally and the rat was killed 8 h later. Glomerular HSGAG was isolated and its size and charge was determined by liquid chromatography. The HSGAG 35sulfate uptake was higher in IL8-treated rats than controls (387+/-138 vs. 246+/-15 cpm/1,000 glomeruli, mean +/- SD, P<0.05). No differences in HSGAG size were observed between IL8-treated and control animals. However, after ion exchange chromatography, there was a shift to the left in the elution profile of IL8-treated rats, demonstrating the presence of chains with decreased negative charge. IL8 infusion into rats results in a decreased total negative charge of the HSGAG. Because IL8 has been found in the serum of some patients with minimal lesion nephrotic syndrome, this finding may explain, at least in part, the reported reduced glomerular charge barrier observed in these patients.

Anti-interleukin 8 antibody abolishes effects of lipoid nephrosis cytokine.

Supernatant factor from peripheral blood mononuclear cell (PBMC) cultures of idiopathic minimal lesion nephrotic syndrome (IMLNS) patients in relapse induces in vivo albuminuria and increases 35sulfate uptake by glomerular basement membrane (GBM) in rats. The purpose of this study was to evaluate the effect of anti-interleukin 8 (IL8) neutralizing antibody on the effects induced by the supernatant factor. Supernatant factor collected from six cultures of PBMC from IMLNS patients in relapse were combined and aliquotted into two samples. Anti-IL8 neutralizing antibody (750 ng) was added to one. Supernatant factor or supernatant factor and anti-IL8 antibody were infused for 5 days into the left renal artery of Wistar rats using an osmotic pump. On the last day of infusion, rats were injected with 35sulfate (1.0 mCi/200 g) intraperitoneally and killed after 8 h. Glomeruli were isolated and GBM obtained. There was a significant increase in 35sulfate uptake of the infused kidney (169 +/- 52 cpm/mg dry glomerular weight, mean +/- SEM) compared with the uptake seen in the contralateral kidney (116 +/- 41, P < 0.05) when the supernatant factor was infused alone. No significant differences in 35sulfate incorporation were seen between infused kidney (173 +/- 5) and contralateral kidney (190 +/- 49) when supernatant factor and anti-IL8 antibody were administered. A significant increase in albuminuria was seen on the last day of infusion (0.43 +/- 0.11 albumin/ creatinine ratio, mean +/- SEM) compared with the ratio prior to infusion of the supernatant factor alone (0.18 +/- 0.03, P <0.05). No significant differences in urinary albumin/creatinine ratios prior to and on the 5th day of infusion were seen when the supernatant factor was administered with anti-IL8 antibody. Supernatant factor effects were abolished by the addition of anti-IL8 neutralizing antibody, suggesting that the described effects are mediated by IL8.

Primary vesicoureteral reflux: review of current concepts.

The well-known association between vesicoureteral reflux and urinary tract infection is the basis for pathophysiological and therapeutic implications which have dominated the literature on the subject for the last 2 decades. We critically review the following issues: (1) does urinary tract infection cause reflux? (2) does reflux predispose to infection? (3) does reflux predispose to pyelonephritis? (4) does reflux predispose to a renal parenchymal scar? (5) does long-term urinary antibiotic prophylaxis prevent renal damage in patients with reflux? We conclude that none of the reviewed issues have been rigorously proven or validated and that the role of vesicoureteral reflux in urinary tract infections needs to be redefined through well-designed, multicenter, prospective, randomized, controlled studies using state of the art renal imaging techniques.

Effect of interleukin-8 on glomerular sulfated compounds and albuminuria.

To evaluate the effect of interleukin-8 (IL8) on glomerular basement membrane (GBM) sulfated compounds and albuminuria, we infused IL8 in 1% bovine serum albumin (BSA) for 5 days into the left renal artery of Holtzman male rats at the rate of 10 microliters/h using an osmotic pump. Control rats received 1% BSA. A significant increase in urinary albumin/creatinine ratio was seen on the last day of IL8 infusion (0.38 +/- 0.11, mean +/- SEM) when compared with albumin/creatinine ratio prior to infusion (0.19 +/- 0.04, P = 0.04). No significant differences in urinary albumin excretion prior to and after infusion of 1% BSA were observed. On the last day of infusion, rats were injected with 35sulfate (1.0 mCi/200 g body weight) intraperitoneally and killed after 8 h. Glomeruli were isolated and GBM obtained. After 5 days of IL8 administration, there was a significant increase in 35sulfate uptake by GBM of the infused kidney (76 +/- 10 cpm/dry glomerular weight, mean +/- SEM) compared with the uptake seen in the contralateral kidney (53 +/- 9, P = 0.05). The in vivo infusion of IL8 increased the 35sulfate uptake by GBM and augmented the urinary albumin/creatinine ratio, suggesting that IL8 may induce albuminuria by altering the metabolism of the GBM sulfated compounds. This hypothesis needs to be confirmed by studies on glomerular charge selectivity and GBM anionic sites during the course of the infusion. Moreover, the persistence of the effect needs to be evaluated by prolonging the infusion for more than 5 days.

Nutritional intake in children with renal insufficiency: a report of the growth failure in children with renal diseases study.

OBJECTIVE: This study was designed to assess sequentially the nutrient intake in children with chronic renal insufficiency and its relationship to body size, the level of renal failure, and growth velocity. METHODS: The nutrient intake from 401 4-day food records obtained from 120 children with renal insufficiency over a 6-month observation period was analyzed. The height and weight were measured at the beginning and end of the observation period. The glomerular filtration rate was estimated from the height and serum creatinine. RESULTS: The mean caloric intake in these children was 80 +/- 23% (mean +/- SD) of the Recommended Dietary Allowance (RDA) for age. Fifty-six percent of the food records obtained from these children revealed a caloric intake that was less than 80% of the RDA. Caloric intake expressed as the %RDA for age decreased with increasing age. However, the mean caloric intake when factored by body weight was in the normal range. There was no correlation between caloric intake and height velocity. The mean protein intake in these children was 153 +/- 53% of the RDA. Further, 45% of the food records indicated a protein intake greater than 150% of the RDA. There was no relationship between the degree of renal insufficiency and caloric or protein intake. Calcium, vitamin, and zinc intakes were also low. CONCLUSIONS: Children with chronic renal failure consume less calories than their age matched peers, but the majority of these children appear to ingest adequate amounts for their body mass. This reduction in caloric intake occurs early in renal insufficiency. They also ingest inadequate amounts of calcium, zinc, vitamin B6, and folate.

Effect of lipoid nephrosis cytokine on glomerular sulfated compounds and albuminuria.

Supernatants from peripheral blood mononuclear cells cultures of 30 idiopathic, minimal lesion, nephrotic syndrome (IMLNS) patients in relapse and the same patients in remission were fractionated by gel filtration chromatography. Fractions eluting with carbonic anhydrase (29 kilodaltons) were infused for 5 days at the rate of 10 microliters/h into the left renal artery of Wistar rats using an Alzet osmotic pump. On the last day of infusion, rats were injected with 35sulfate (1.0 mCi/200 g) intraperitoneally and killed after 8 h. Glomeruli were isolated and glomerular basement membrane (GBM) obtained. There was a significant increase in 35sulfate uptake by GBM of the infused kidney (302 +/- 92 cpm/mg dry glomerular weight, mean +/- SEM) compared with the uptake seen in the contralateral kidney (157 +/- 36, P < 0.01) when the fraction from IMLNS patients in relapse was infused. No significant differences in 35sulfate incorporation were seen between infused kidney (166 +/- 41) and contralateral kidney (172 +/- 64) when the same fraction from patients in remission was administered. A significant increase in albuminuria was seen on the last day of infusion (14.2 +/- 1.0 mg/24 h, mean +/- SEM) when supernatant factor from IMLNS patients in relapse was used. No significant differences in urinary albumin excretion prior to and after infusion were seen when the same fraction from IMLNS patients in remission was administered. The in vivo infusion of supernatant factor from IMLNS patients in relapse increased the 35sulfate uptake by GBM and augmented albuminuria, suggesting that the factor may have pathogenic significance in the proteinuria of IMLNS.

The effect of lymphocytes from renal transplant patients on glomerular basement membrane sulfate uptake.

We have studied the effect of peripheral blood mononuclear cells (PBMC) from renal transplant patients on 35sulfate uptake by rat glomerular basement membrane (GBM). Nine patients were included in the study; six were studied during an episode of acute allograft rejection and seven while not undergoing acute rejection. The sulfate uptake index, calculated as the ratio between uptake by GBM from rat glomeruli cocultured with PBMC and 35sulfate incorporation by GBM from glomeruli cultured alone, was significantly higher when glomeruli were cocultured with PBMC from patients undergoing an acute rejection (3.26 +/- 1.18, mean +/- SEM) than it when glomeruli were cocultured with PBMC from nonrejecting transplant patients not showing proteinuria (0.81 +/- 0.11) (P = 0.0053). After reversing the acute allograft rejection with resolution of proteinuria, the sulfate uptake index returned to normal in four of five patients. The fifth patient had persistent nephrotic syndrome and his sulfate uptake index remained elevated. These findings are similar to those observed in idiopathic minimal lesion nephrotic syndrome patients in relapse. Because the GBM sulfated compounds may play a role in glomerular permeability to plasma proteins, by acting on these compounds PBMC may be a common mechanism for proteinuria.

Effect of lymphokines on 35sulfate uptake by the glomerular basement membrane.

We have previously shown that lymphocytes from idiopathic minimal-lesion nephrotic patients produce a lymphokine (supernatant factor) that increases the 35sulfate uptake in the glomerular basement membrane (GBM). The purpose of this report was to further characterize the supernatant factor by studying the effects of interleukins (IL) 2-4, 6, and 8, granulocyte-macrophage colony stimulating factor, and tumor necrosis factor on the 35sulfate incorporation by rat glomeruli in vitro. A significant increase in GBM 35sulfate uptake was only seen when the glomeruli were cultured with the addition of IL-8 as compared with control cultures: 10.8 +/- (SEM) 1.7 and 7.9 +/- 1.4 cpm/micrograms GBM protein, respectively (p < 0.005). IL-8 reproduces the effect of the reported supernatant factor on the GBM 35sulfate uptake. Because IL-8 was detected in the supernatant of peripheral mononuclear cell cultures from idiopathic minimal-lesion nephrotic syndrome patients in relapse and because the increased GBM 35sulfate incorporation induced by the supernatant factor has been abolished by the addition to the culture media of anti-IL-8 neutralizing antibodies, we postulate that IL-8 is the previously described supernatant factor.

IL-8 production by peripheral blood mononuclear cells in nephrotic patients.

We studied the interleukin 8 (IL-8) gene expression by peripheral blood mononuclear cells (PBMC) and the IL-8 serum concentration in patients with idiopathic minimal lesion nephrotic syndrome (IMLNS) and other glomerulopathies. PBMC from eight of the nine (IMLNS) patients in relapse demonstrated the presence of IL-8 mRNA. All three IMLNS patients in remission (P = 0.0026 when compared to patients in relapse) and the two patients with nephrotic syndrome with other glomerulopathies failed to elicit an IL-8 mRNA response. Eleven of the 12 IMLNS patients in relapse showed IL-8 serum concentration above the level of detection. Only one of the seven patients in remission had detectable serum levels of IL-8 (P = 0.0033 when compared to levels from IMLNS patients in relapse). IL-8 serum levels were not detectable in three patients with nephrotic syndrome and other glomerulopathies. Supernatants of PBMC cultures from IMLNS patients in relapse increased the 35sulfate uptake by rat GBM. This effect was abolished by the addition of anti-IL-8 neutralizing antibody to the culture media and reproduced by the addition to the media of IL-8 in concentrations found in the serum of IMLNS patients in relapse. Finally, the effect of IL-8 on the 35sulfate turnover of the glomerular basement membrane (GBM) sulfated compounds was evaluated in vitro. A significant decrease in the percentage of residual 35sulfate incorporated in the GBM (41 +/- 5, mean +/- SEM) was observed in cultures treated with IL-8 as compared to those that were not treated with IL-8 (58 +/- 8, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Early presentation of tuberous sclerosis as bilateral renal cysts.

We report on an infant in whom bilateral renal cysts were the only initial manifestation of tuberous sclerosis. We review the reported cases of infants with this association and emphasize that tuberous sclerosis can present in infancy as bilateral renal cystic disease. The role of the kidney biopsy in providing the correct diagnosis is discussed.

Membranous nephropathy associated with multiple sclerosis.

Membranous nephropathy and multiple sclerosis are believed to be mediated by immune mechanisms. A patient is reported with the first described association of membranous nephropathy and multiple sclerosis. Its significance and possible pathogenetic mechanisms are discussed.

Therapy of renal anemia in children and adolescents with recombinant human erythropoietin (rHuEPO).

Eleven anemic children and adolescents with a median age of 14 years (range six months-20 years) on chronic hemodialysis were treated with recombinant human erythropoietin (rHuEPO) intravenously three times a week for an average of 9.2 months. After eight weeks of therapy, hematocrit rose from 20.3 +/- 1.4% to 31.7 +/- 0.7% (0.20 +/- 0.01 to 0.31 +/- 0.007, p less than 0.001, mean +/- SEM). After reaching the target hematocrit of 30% to 33% (0.30 to 0.33), doses were adjusted individually. Blood transfusions were eliminated in all but one patient. All patients experienced an increase in appetite and energy level. Serum ferritin concentrations decreased in all patients who reached target hematocrit and seven required iron supplementation. Hypertension worsened in two patients and developed in two others. One patient's vascular access clotted. Dialysis efficiency and heparin requirements during dialysis did not change significantly. We conclude that rHuEPO is safe, effective, and should be recommended as treatment for anemia in children and adolescents on hemodialysis, but close monitoring for the development of hypertension and/or iron deficiency is necessary.

Effect of lymphokine from nephrotic peripheral blood mononuclear cells on catabolism of rat glomerular basement membrane sulfated compounds.

We have previously shown a significant increase in sulfate-35 uptake in rat glomerular basement membrane (GBM) when glomeruli were cultured with peripheral blood mononuclear cells (PBMC) from patients with idiopathic minimal lesion nephrotic syndrome (IMLNS) in relapse. In the present study, we have isolated the lymphokine mediating the augmented sulfate-35 incorporation and evaluated its effect on the catabolism of the GBM sulfated compounds. Supernatants from IMLNS PBMC cultures of 13 patients in relapse and 10 in remission were fractionated using gel filtration chromatography. There was a significant increase in rat GBM sulfate-35 uptake when glomeruli were cultured in carbonic anhydrase fraction from patients in relapse (12.9 +/- 3.2; cpm/microgram GBM protein, mean +/- SEM) as compared to glomeruli cultured in the same fraction from patients in remission (8.2 +/- 2.5: cpm/microgram GBM protein; p < 0.05). The catabolism of the GBM sulfated compounds was determined by studying the washout of the sulfate-35 macromolecules after equilibration in sulfated isotope-free medium for 12 h. There was a significant decrease in residual sulfate-35 in rat GBM when glomeruli were cultured in a 29-kD fraction from patients in relapse (7.0 +/- 2.5; cpm/micrograms GBM protein, mean +/- SEM) as compared to glomeruli cultured in the same fraction from patients in remission (31.8 +/- 1.6; p < 0.005). No significant differences in sulfate-35 incorporation were seen when other fractions from patients in relapse and in remission were compared. These studies suggest that the lymphokine secreted by PBMC from IMLNS patients in relapse increases the catabolism of the GBM sulfated compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary prostaglandin E2 in patients with vesicoureteral reflux.

The urinary prostaglandin E2 (PGE2) excretion of children with various grades of vesicoureteral reflux who were undergoing reimplant surgery was compared to those of age- and sex-matched controls. Urinary PGE2 excretions were significantly increased in patients with vesicoureteral reflux (p = 0.001). Furthermore, the PGE2 excretion correlated positively with the grade of reflux. Because of the interaction between vasopressin, sodium excretion, and PGE2, elevated urinary PGE2 may partially explain the decreased concentrating capacity seen in children with vesicoureteral reflux.

Atrial natriuretic factor in idiopathic minimal-lesion nephrotic syndrome.

The plasma levels of atrial natriuretic factor (ANF) were measured both during relapse and remission in 8 patients with idiopathic, minimal-lesion nephrotic syndrome. The plasma levels of ANF were significantly higher in the patients during relapse (53.3 +/- 21.2 pg/ml, mean +/- SEM) as compared to the values observed in the same patients during remission (19.4 +/- 4.1 pg/ml; p less than 0.05). This moderate increase in ANF is not likely to be explained by hypervolemia and is associated with sodium and water retention rather than natriuresis and diuresis.

Insulinlike growth factors in patients with active nephrotic syndrome.

The serum concentrations of insulinlike growth factors 1 and 2 (IGF-1 and IGF-2) were measured by specific radioimmunoassays in 25 nephrotic patients. The serum concentration of IGF-1 in nephrotic patients (mean +/- SEM, 169 +/- 17 ng/mL) was significantly lower than that observed in 20 control subjects matched for sex and age (338 +/- 36 ng/mL). The IGF-2 serum concentration was significantly lower in nephrotic patients (343 +/- 22 ng/mL) than in control subjects (898 +/- 80 ng/mL). The IGF-1 and IGF-2 150-kd and 45-kd carrier protein complexes were found in the urine of nephrotic patients, whereas there was no binding of radiolabeled IGF-1 or IGF-2 to IGF carrier proteins in the urine of control subjects. The low serum IGF-1 and IGF-2 levels observed in nephrotic patients could be partially due to the increased urinary losses of the IGF carrier proteins.

Effect of prednisone on nephrotic peripheral blood mononuclear cell mediated increase in 35sulfate uptake in rat glomerular basement membrane.

We have previously described a significant increase in 35sulfate uptake in rat glomerular basement membrane (GBM) when glomeruli were cocultured with peripheral blood mononuclear cells (PBMC) from patients with idiopathic minimal-lesion nephrotic syndrome (IMLNS) in relapse, but not with PBMC of IMLNS patients in remission. In the present study we examined the effect of prednisone therapy on the PBMC-mediated increase in 35sulfate GBM uptake. The GBM 35sulfate uptake after rat glomeruli were cocultured with PBMC from 11 IMLNS patients in relapse (geometric mean 437 cpm/mg dry glomerular weight) was significantly higher than the incorporation observed in glomeruli cultured alone (geometric mean 229 cpm/mg dry glomerular weight; p less than 0.01). However, no significant differences in 35sulfate uptake were seen between glomeruli cultured alone and glomeruli cocultured with PBMC from IMLNS patients when PBMC were obtained from the 11 patients on treatment with prednisone (2 mg/kg/day) or the same patients in remission and off prednisone therapy. Prednisone therapy abolished the PBMC-mediated increased 35sulfate uptake by rat GBM. GBM sulfated compounds seem to play a role in glomerular permeability. The temporal relationship between inhibition of GBM sulfate incorporation by prednisone and resolution of the proteinuria support the hypothesis that PBMC from IMLNS patients in relapse could secrete a lymphokine which by altering the metabolism of the GBM sulfated compounds may subsequently increase glomerular permeability to plasma proteins.

Cyclosporine therapy for steroid-resistant nephrotic syndrome. A controlled study.

We have conducted a controlled trial on the efficacy of cyclosporine in eight patients with steroid-resistant nephrotic syndrome (four with idiopathic minimal lesion nephrotic syndrome and four with focal segmental glomerulosclerosis). Patients were randomly allocated to a cyclosporine (5 mg/kg/d) or a control group. After eight weeks of therapy and one month without cyclosporine therapy, patients in the control group were given cyclosporine for eight weeks and those in the cyclosporine group became controls. Before the initiation of treatment, there was no difference between the groups with regard to proteinuria and serum albumin levels. Proteinuria remained unchanged in the cyclosporine group, while there was a significant increase in proteinuria in the control group. There were no significant changes in serum albumin levels in either group during the trial. This study does not support the use of cyclosporine at the dose of 5 mg/kg/d in patients with steroid-resistant minimal lesion nephrotic syndrome or focal segmental glomerulosclerosis.