COMPARTMENTAL ARRANGEMENT OF STEROIDS FORMED FROM [1-14C] ACETATE BY RAT ADRENAL ZONA GLOMERULOSA AND THE EFFECT OF CORTICOTROPHIN

Abstract

ABSTRACT Using a technique of incubation with dialysis, the secretion and compartmental arrangement of steroids derived from [3H]pregnenolone, [14C]acetate and from endogenous precursors in rat adrenal capsules (zona glomerulosa) have been studied. In the absence of corticotrophin, 14C-labelled deoxycorticosterone and 18-hydroxydeoxycorticosterone tended to be non-dialysable, whereas the 3H-labelled fractions of these compounds were dialysable. Approximately equal yields of 18-hydroxydeoxycorticosterone and corticosterone were obtained from [14C]acetate, whereas about five times as much corticosterone as 18-hydroxydeoxycorticosterone was formed from [3H]pregnenolone. With the addition of Synacthen to the incubation medium, the 14C-labelled compounds, most noticeably deoxycorticosterone, were released from the bound condition, and at the same time the ratio of [14C]corticosterone to [14C]18-hydroxydeoxycorticosterone altered, and became similar to the ratio for the tritium labelled material. The data suggest that in these respects 14C-labelled steroids derived from [14C] acetate behave similarly to the material formed from endogenous precursors, and in the absence of corticotrophin may exist in a compartment of the zona glomerulosa which is not penetrable by the steroids derived from a later precursor such as [3H]pregnenolone. The two types of steroid have different metabolic fates: bound deoxycorticosterone for example, appears to be equally vulnerable to 11β- and 18-hydroxylation, whereas the free deoxycorticosterone is preferentially 11β-hydroxylated. The mechanism may be involved in the fine control of the secreted products.