Constant Infusion of Hypertonic Saline in the Dog

III. Effects of Physiologic Saline Preloading and of Aldosterone Thereon

Abstract

The characteristic values of renal Na regulatory system were determined during constant infusion experiment of hypertonic saline with and without physiological saline preloading. After physiological saline preloading renal threshold for Na rejection was lowered significantly. Aldosterone could not counteract this lowering of renal Na threshold. It is inferred that Na excretion after elevation of plasma Na concentration is linearly dependent on its concentration under both conditions with and without physiological salin epreloading. This finding is consistent with the single capacitive model of the first report. And aldosterone cannot control augmented overflowing Na rejection induced by conditioning volume and Na preload. This supports the dualistic concept in the renal Na reabsorptive mechanism.