Origin of aldosterone in trypsin-stimulated rat adrenal zona glomerulosa incubations.

The time-course for the in-vitro secretion of aldosterone and 18-hydroxycorticosterone (18-OH-B) by rat adrenal whole capsular tissue (largely zona glomerulosa) was studied under control and stimulated conditions. The stimulatory effect of trypsin was relatively delayed, and the steroids were significantly enhanced only after 1 h, in contrast to the actions of ACTH, which produced effects after 15 or 30 min. Tissue-sequestered 18-hydroxydeoxycorticosterone (t-18-OH-DOC), which is not affected by ACTH, was significantly depleted by trypsin, but secreted 18-OH-DOC was not consistently affected by either stimulant. In contrast to the apparent mobilization of t-18-OH-DOC, the conversion of exogenously added [3H]18-OH-DOC to [3H]18-OH-B was inhibited by trypsin, and aldosterone was unaffected. When trilostane was added to inhibit de-novo steroidogenesis, under conditions in which the steroid secretory response to ACTH is completely inhibited, aldosterone and 18-OH-B secretion was still stimulated by trypsin although yields were lower. Compared with controls, trilostane reduced t-18-OH-DOC concentrations, and trypsin caused a further depletion. In other studies, glomerulosa plasma membrane enriched preparations were homogenized and centrifuged, and the supernatants were dialysed and added to incubations of dispersed zona glomerulosa cells in the presence or absence of stimulators of aldosterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)