Stop Flow Analysis of Aldosterone and Steroidal Antagonist SC-8109 on Renal Tubular Sodium Transport Kinetics.

Abstract

In normal dogs the distal tubule can lower Na concentration almost to zero during stop flow, the minimal concentration achieved being independent of plasma Na concentration. In adrenalectomized animals, minimal distal concentrations achieved are not as low. As plasma Na is increased, minimal distal Na concentration also increases in direct proportion, indicating that adrenalectomy reduces maximal Na concentration gradient which can be maintained across distal tubular cells. Results in adrenalectomized and in SC-8109 treated dogs are identical. Administration of cortisone to adrenalectomized dogs does not repair this defect, but aldosterone restores ability of the distal tubule to lower Na concentration, even in presence of elevated plasma Na. Aldosterone when given to adrenalectomized dogs did not alter proximal Na reabsorption, as this can be estimated by stop flow data.