Chemical medullectomy does not prevent sodium retention in nephrotic rats.

Experiments were performed to study the effect of chemical medullectomy on the renal retention of sodium in rats with an experimental nephrotic syndrome. Nephrosis was induced in rats by a single injection of puromycin aminonucleoside (PAN) and the renal excretion of water and electrolytes was monitored for 11 days. Sodium output in nephrotic rats fell to approximately 10% of control levels and exchangeable body sodium increased to 54.6 +/- 2.7 mM/kg compared with 41.5 +/- 0.8 mM/kg in controls. The animals had edema and ascites and there was a 35% increase in plasma volume and a corresponding fall in hematocrit. Severe structural and functional damage to the inner renal medulla induced by the injection of bromoethylamine hydrobromide (BEA) resulted in little change in the pattern of sodium and water retention caused by PAN alone. Exchangeable body sodium in rats treated with PAN and BEA was 51.5 +/- 3.8 mM/kg. It is concluded that an intact inner renal medulla is not necessary for sodium retention to occur in PAN nephrosis in rats.