EFFECT OF POTASSIUM INTAKE ON THE FINAL STEPS OF ALDOSTERONE BIOSYNTHESIS IN THE RAT

Abstract

ABSTRACT Incubated capsular adrenal glands (»zona glomerulosa«) of potassiumdeficient rats converted approximately 30 times less tritiated corticosterone to aldosterone and 18-hydroxycorticosterone than capsular adrenals of potassium-replete rats. This difference was demonstrable over a large range of substrate concentrations. Capsular adrenal mitochondria of potassium-deficient rats also incorporated considerably less tritiated corticosterone into aldosterone and 18-hydroxycorticosterone than mitochondria of potassium-replete rats. Conversion to both corticosteroid fractions increased within 4 hours and became normal within 24 hours of resumed potassium intake. On the other hand, potassium intake only marginally affected the ratio of 18-hydroxycorticosterone formation to aldosterone formation by capsular adrenals and had no effect on the conversion of tritiated deoxycorticosterone to 18-hydroxydeoxycorticosterone and 18-hydroxycorticosterone by decapsulated adrenals (»zona fasciculata-reticularis« These findings indicate that potassium intake enhances 18-hydroxylase activity selectively in the zona glomerulosa of the rat adrenal cortex, but yield no information concerning an effect on 18-hydroxydehydrogenase activity. Kinetic data suggest that the potassium-induced increase in 18-hydroxylase activity is most likely due to de novo enzyme synthesis.