Renin and aldosterone secretions during hypovolemia in rats: relation to NaCl intake

Abstract
Plasma renin activities (PRA) and aldosterone concentrations increased in parallel over a wide range of plasma volume deficits produced in unanesthetized rats by extravascular administration of polyethylene glycol (PEG) solution. When PEG-treated rats were given water to drink, their intakes were proportional to PRA; when given water and 0.5 M NaCl, PRA and the steroid concentrations diminished concurrently in association with Na consumption. Aldosterone concentrations and NaCl intakes were markedly enhanced after PEG treatment in rats maintained on a Na-deficient diet for 4 days. A clear relation between PRA and water intake, and between circulating aldosterone levels and Na intake, was not suggested by other experiments in this series. For example, bilateral nephrectomy abolished the rise in PRA during hypovolemia yet rats drank water normally. Aldosterone concentrations were substantially elevated by PEG treatment in the nephrectomized rats yet Na appetite was abolished. Neither angiotensin nor aldosterone plays a prominent role in stimulating water and saline intakes during hypovolemia.