Short-term effect of aldosterone on renal sodium transport and tubular Na-K-ATPase in the rat.

The short-term effect of one single injection of aldosterone on the renal sodium transport on one hand, and the Na-K-ATPase activity on the other hand, was studied in chronic adrenalectomized rats. Sodium transport was estimated by clearances, and Na-K-ATPase was measured in microdissected fragments of the nephron, according to our microtechnique previously described. Five to eight days after adrenalectomy, only 30% of the initial enzyme activity was recovered in the cortical collecting tubule (CCT). Administration of aldosterone completely restored the ATP-ase activity within three hours. Adrenalectomy also curtailed by 20-45% the activity of other nephron segments but aldosterone had no stimulatory effect on them. Sodium-reabsorption also increased after the hormone injection, following the same time (0.5 less than t1/2 less than 1 h) and dose dependencies (0.8 less than K1/2 less than 0.9 micrograms/kg) as those observed for the enzyme activity in the CCT. It is concluded that the short-term stimulation of Na-K-ATPase in the collecting tubule, after an acute administration of aldosterone, may be responsible for the simultaneous increase in sodium transport.