Intrathrombic urokinase reverses neonatal renal artery thrombosis.

A term infant with aortic and renal artery thrombosis is described, in whom the right kidney experienced complete ischemia for 5 days. A continuous intrathrombic urokinase infusion induced complete clot lysis and reperfusion of the right kidney. Follow-up studies of renal function and renal growth have been normal. This is the first report to describe complete pharmacological salvage of a neonatal kidney after prolonged warm ischemia. This case underscores both the ability of the neonatal kidney to recover from prolonged ischemia and the need to effect thrombolysis before irreversible renal injury occurs. The intrathrombic use of fibrinolytic agents in similarly affected infants warrants consideration and further study.

Growth hormone regulates ammoniagenesis in canine renal proximal tubule segments.

To determine whether growth hormone (GH) directly affects ammoniagenesis in the renal proximal tubule, ammonia production was measured in suspensions of isolated canine renal proximal tubule segments (IPTs) incubated with 2.5 mM L-glutamine and varying concentrations of human growth hormone (hGH). Ammonia production from IPTs significantly increased by nearly threefold in the presence of hGH (10(-6) M) at 60 min. This increase was dose dependent, with as little as 10(-9) M hGH significantly stimulating ammonia production. In addition, hGH enhanced glucose production when lactate, alanine, and succinate replaced L-glutamine as substrate. hGH significantly stimulated ammonia production when IPTs were incubated at alkalotic and neutral pH. The effect of hGH was lost at acidic pH. When hGH was added to IPTs incubated under Na(+)-equilibrated conditions, ammonia production was not different from control. hGH stimulated ouabain-sensitive Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity by 8.1 +/- 1.1% in basolateral membranes isolated from IPTs. hGH stimulation of proximal tubule ammonia production from L-glutamine occurs at physiological concentrations of hGH and when the extracellular-to-intracellular Na+ gradient favors L-glutamine transport. This effect is associated with an increase in basolateral Na(+)-K(+)-ATPase activity. The data suggest a role for hGH in the regulation of renal acid-base metabolism under physiological conditions in which increased net acid excretion is important.

Progressive renal insufficiency in methylmalonic acidemia.

Methylmalonic acidemia is a heterogeneous inborn error of propionate metabolism. Therapy frequently includes a low-protein diet to minimize precursors of methylmalonic acid (MMA) and reduce its concentration in body tissues. Renal dysfunction in these patients is increasingly recognized. Tubulointerstitial disease has been found in the small number of renal biopsy specimens from young children previously reported by others. We describe an 18-year-old patient with the mut- form of the disease who developed renal dysfunction despite the use of a low-protein diet. Tubulointerstitial injury was documented by renal biopsy. The patient had no risk factors associated with established causes of chronic tubulointerstitial nephropathy (CTIN). We postulate that methylmalonyl-CoA and/or its precursors (propionyl-CoA, odd-chain fatty acids), may be capable of producing CTIN. We speculate that prevention of renal injury may require lower tissue levels of MMA and its precursors than those required for prevention of ketoacidosis.