Prolonged oral administration of potassium upon aldosterone biosynthesis by rat glomerulosa tissue in vitro

Steroid production rate of adrenals derived from rats drinking a 0.3 M KC1 + 5% glucose solution for 7 days was compared to that of control rats drinking a 5% glucose solution in order to investigate the effect of potassium loading upon the early and late step of aldosterone biosynthesis. Following potassium loading the quartered adrenals produced more aldosterone but less corticosterone as compared to the control. Potassium loading resulted in an increased aldosterone production rate by capsular adrenals (z. glomerulosa) provided that the corticosterone concentration in the incubation medium was elevated either by incubating it together with the decapsulated adrenal or adding exogenous corticosterone (4--16 mug/ml) to the medium. The corticosterone to aldosterone converting capacity of capsular adrenals is markedly higher in the potassium-loaded rats than in the controls. In the first 15 minutes of incubation the corticosterone production rate of the two groups was equal, aldosterone production rate by capsular adrenals of potassium-loaded rats, being higher than that of control animals. Corticosterone output of capsular adrenals from potassium-loaded rats decreased more rapidly in course of the incubation than it did in control tissue. These results suggest that the increase in aldosterone secretion in vivo following potassium loading is due to the stimulation of conversion of corticosterone to aldosterone in the glomerulosa cells. However, the endogenous corticosterone production during the incubation of glomerulosa cells from pottasium-loaded rats decreases so rapidly that the cells are not capable of producing more aldosterone than the control ones in spite of activated 18-hydroxylase.