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A new method for the assessment of endogenous formation of aldosterone in anephric patients is described. (1, 2-3H) aldosterone was administered i.v. to patients 1-2 days before hemodialysis, and then the specific activity (SA) of tetrahydroaldosterone glucosiduronate, the major aldosterone metabolite, was measured in the dialysate using a specific radioimmunoassay. The aldosterone secretion rate was determined from the extent of isotope dilution by endogenous metabolite. Aldosterone secretion rates measured in 10 patients were for the most part low. The secretion rate determined in blood from the aldosterone metabolic clearance rate and plasma aldosterone concentration closely approximate secretion rate values obtained by the isotope dilution method in 3 of 4 patients. In 2 patients in whom ACTH was administered chronically, radio-labeled aldosterone was administered at the start of the study and then the day to day aldosterone secretory response to ACTH was determined from the SA of tetrahydroaldosterone in blood. Aldosterone secretion continuously increased for as long as ACTH was administered.

The effect of sodium intake on the aldosterone metabolic clearance rate (MCR) was examined in 5 normal subjects. Measurements were made under conditions where dietary sodium ranged from 10 to 1500 meq/day. There were no consistent changes in MCR over these extremes of sodium intake, and the plasma level of aldosterone correlated only with the aldosterone urinary excretion rate. In an additional group of 6 normal subjects, a single dose of 100 meq sodium administered orally had no effect on the aldosterone MCR. The findings indicate that aldosterone metabolism is unaffected by sodium intake.