Immunotactoid glomerulopathy in sickle cell anemia.

A 12-year-old African American male with homozygous sickle cell disease (SCD) was admitted with insidious onset of periorbital and scrotal edema. The initial evaluation failed to reveal any underlying monoclonal gammopathy, or cryoglobulinemia, or other systemic causes for the renal disease. A percutaneous renal biopsy was consistent with immunotactoid glomerulopathy (ITG), which is rare in children and is characterized histologically by fibrillar deposits in the glomeruli. Children can present with symptoms of nephrotic syndrome and progress to end stage renal disease. Our patient was treated with an ACE inhibitor and is currently free of edema and with normal renal function on follow-up at 1 year. Immunotactoid glomerulopathy should be considered in the differential diagnosis of nephrotic syndrome in children with sickle cell disease. Renal biopsy is indicated in children with sickle cell disease and nephrotic syndrome and ITG should be considered as potential cause. Although there is no effective treatment for this condition, ACE inhibitors can decrease the protein-uria and possibly delay the progression to end stage renal disease. The side effects related to the use of ACE inhibitors should be monitored. These include renal impairment, hyperkalemia, anemia, neutropenia, and angioedema. Since we have a short follow-up in our patient, the role and safety of ACE inhibitors in the management of ITG need further evaluation.

Prenatal programming of adult hypertension in the rat.

BACKGROUND: Epidemiological studies have suggested that low birthweight is a risk factor for the development of essential hypertension in adulthood, but the mechanism is unknown. METHODS: A rat model of intrauterine growth retardation was employed. Pregnant Sprague-Dawley rats were kept on 6% protein or on control isocaloric 20% protein diet from gestational day 12 until term. Systolic blood pressures of the offspring were monitored by the tail cuff method. Apoptosis was determined by the TUNEL method, cell proliferation by anti-Ki67 antibody, and the total number of glomeruli by the maceration method. Results are mean +/- SD. RESULTS: The kidney and body sizes of the offspring from the low-protein pregnancies (LP) were proportionately decreased at birth. Full catch-up growth occurred during the first two weeks of life. The kidneys were normal by standard histology but exhibited increased apoptosis without increased cell proliferation at eight weeks of age. The total number of glomeruli per kidney was decreased by 28% in males (P < 0.001) and by 29% in females (P < 0.01). By eight weeks of age, both male and female LP had systolic blood pressures that were 20 to 25 mm Hg higher than those of control animals (P < 0.001), and their 18-month survival was significantly decreased (44 vs. 93%, P < 0.01). During the prehypertensive stage, at four weeks of age, PRA in LP was low (1.7 +/- 1.4 vs. 19.7 +/- 5.5 ng/mL/hour in males, P < 0.0001; 4.9 +/- 2.2 vs. 14.9 +/- 7.2 ng/mL/hour in females, P < 0.0005), and aldosterone was high (93 +/- 15 vs. 54 +/- 27 pg/mL in males, P < 0. 005; 93 +/- 20 vs. 48 +/- 20 pg/mL in females, P < 0.0001). Smaller but significant differences persisted at eight weeks of age. CONCLUSIONS: Adult blood pressure profile is susceptible to prenatal programming by maternal low-protein diet in the rat. The mechanism may involve an altered renin-aldosterone axis and a deficit in total nephron number.

Syndrome of hypokalemic metabolic alkalosis and hypomagnesemia associated with gentamicin therapy: case reports.

Nephrotoxicity, as evidenced by renal insufficiency is a well-known consequence of gentamicin therapy. We report two patients with gentamicin-induced syndrome of hypokalemic metabolic alkalosis and hypomagnesemia. Both had complete recovery of renal tubular function after cessation of antibiotic therapy. These cases emphasize the need to routinely monitor patients receiving gentamicin therapy for electrolyte abnormalities to avoid potential morbidity.

Biphasic effects of dopamine on 86rubidium uptake in rat renal proximal tubules.

The mechanism(s) by which dopamine inhibits Na+-K+-ATPase activity in the renal proximal tubule is still controversial. We studied the short-term effects of dopamine on the sodium pump in rat renal proximal tubule suspensions with the 86Rb uptake method. Dopamine and the D1-like agonist, SKF81297, initially stimulated Na+-K+-ATPase activity at 5 min and subsequently inhibited it at 10 min and 20 min; the inhibition by 10 microM dopamine at 20 min was 21.3 +/- 4.5%. The inhibitory effect of dopamine on Na+-K+-ATPase activity was mimicked by thymeleatoxin (a classical protein kinase C [PKC] agonist) while Sp-8-CPT-cAMPS (a protein kinase A [PKA] agonist) had no effect. However, the combination of the PKC and PKA agonists mimicked the biphasic effects of dopamine and SKF81297. Rp-8-CPT-cAMPS (a PKA inhibitor), U-73122 (a phospholipase C inhibitor), or calphostin C (a PKC inhibitor), blocked the dopamine-mediated biphasic effects on Na+-K+-ATPase activity. It is suggested that the biphasic effects of dopamine on Na+-K+-ATPase activity (an initial stimulation and a subsequent inhibition) are transduced by activating both PKA and PKC through a D1-like receptor.

Aggressive treatment of severe idiopathic focal segmental glomerulosclerosis.

When focal segmental glomerulosclerosis (FSGS) has reached the stage of chronic renal insufficiency, further progression is usually considered inevitable. African-American patients are believed to exhibit a particularly aggressive form of FSGS. We have treated five African-American patients, aged 11-18 years, with FSGS and reduced renal function using intensive intravenous methylprednisolone protocol, combined with chlorambucil in three cases. All patients had a pretreatment creatinine clearance of less than 50 ml/min per 1.73 m2. Three patients responded with normalization of creatinine clearance and serum albumin levels and had no or only minimal proteinuria at latest follow-up. One patient showed no improvement and one patient progressed to end-stage renal disease. These findings indicate, for the first time, that even severe FSGS may respond to aggressive methylprednisolone with or without alkylating agent treatment, and that African-American race does not preclude a favorable response.

Nephrotic syndrome associated with Toxocara canis infection.

This case report describes nephrotic syndrome in a 7-year-old boy coincident with Toxocara canis infection. This rare association was confirmed by elevated Toxocara-specific IgM titres. Treatment with corticosteroids resulted in remission of renal symptoms as well as abatement of the T. canis infection. The relationship between T. canis infection and glomerular disease is still unclear; nephrotic syndrome may be another manifestation of T. canis infection.

Developmental regulation of ENaC subunit mRNA levels in rat kidney.

To assess the role of distal nephron apical Na channel (ENaC) gene expression in Na wasting by the immature kidney, ENaC alpha-, beta-, and gamma-subunit mRNA levels were examined in the rat by RT-PCR. In microdissected nephron segments, all three ENaC subunit mRNAs were detected in the distal convoluted tubule, connecting tubule, cortical collecting duct, and outer medullary collecting duct. The inner medullary collecting duct and all other nephron segments were consistently negative. The mRNA levels were quantified in kidneys at different developmental stages by multiplex RT-PCR with "primer dropping," with endoplasmic reticulum-specific cyclophilin mRNA as an internal standard. All three ENaC mRNA levels were low or undetectable on gestational day 16 and only slightly higher 3 days before birth. A sharp rise was observed between 3 days before and 1-3 days after birth; the levels at postnatal days 1-3 were already similar to those of adult kidneys. The results suggest that ENaC subunit gene expression is not a limiting factor in the full-term newborn rat kidney, but low levels of expression may limit distal Na absorption in more immature kidneys, such as those of very premature human infants.

Dopamine and protein phosphatase activity in renal proximal tubules.

In the brain, dopamine, via protein kinase A (PKA) activation of dopamine- and cAMP-regulated phosphoprotein (DARPP-32), inhibits protein phosphatase 1 (PP1) activity and keeps Na(+)-K(+)-adenosinetriphosphatase (ATPase) in its phosphorylated inactive state. In the present study, we examined the relationship among dopamine, PP1, and Na(+)-K(+)-ATPase activities in renal proximal tubules. PP1 activity in proximal tubules was not decreased by dopamine (5 x 10(-9)-10(-4) M), fenoldopam (5 x 10(-6) M), or norepinephrine (5 x 10(-7) M). In contrast, in the medullary thick ascending limb of Henle and in the brain striatum, PP1 activity was decreased by fenoldopam (5 x 10(-6) M). We also showed that the ability of dopamine (10(-6) M) to inhibit Na(+)-K(+)-ATPase activity in proximal tubules (assessed by ouabain-sensitive 86Rb uptake) occurred in the absence or presence of a sodium clamp with 5 microM monensin. Thus the inhibitory effect of dopamine on Na(+)-K(+)-ATPase activity in proximal tubules is not regulated by PP1 activity. Tautomycin and okadaic acid by themselves, at concentrations that inhibited PP1 activity, had no effect on Na(+)-K(+)-ATPase activity in proximal tubules. The ability of a dopamine D1 agonist, fenoldopam, to inhibit PP1 activity in brain striatum and in medullary thick ascending limb, but not in proximal tubules, suggests differential organ and nephron segment regulation of PP activity.

Evaluation of renal function.

Renal function can now be evaluated in utero and after birth. Most of the methods used to investigate suspected renal dysfunction or disease are not presently applicable to the fetus; however, prenatal and postnatal evaluation of renal function has assumed a greater importance as the consequences of birth before term become more apparent.