Renin release and the refractoriness to acute renal failure of rats recovering from prior renal failure.

Renin substrate concentrations and the release of renin in response to the rapid removal of 15 ml/kg weight blood or subcutaneous administration of 500 microgram/kg body weight isoproterenol were measured in control rats and animals recovering from prior myohemoglobinuric acute renal failure (recovery rats). Blood for these assayas was drawn from chronically implanted aortic catheters, obviating the need for animal handling and anesthesia. Baseline plasma renin titers of recovery rats were modestly elevated but renin substrate concentrations were the same as in controls. Hemorrhage produced equivalent changes in blood pressure and plasma renin titer in the two groups. Isoproternol injection in recovery rats caused a somewhat greater blood pressure fall and almost twice the rise in plasma renin concentration observed in control rats. The marked resistance of recovery animals to a second bout of acute renal failure thus cannot be attributed to impaired renin release or inadequate plasma renin substrate.