Factors affecting the trypsin induced release of aldosterone in rat adrenal zona glomerulosa tissue

Abstract

The yields of aldosterone obtained during incubation of whole adrenal capsule tissue from the rat (consisting of the connective tissue capsule itself, all of the glomerulosa tissue, and some fasciculata) cannot apparently be accounted for by the gland's capacity for de novo synthesis of this steroid. Recent studies with proteolytic enzymes and inhibitors suggest that in part aldosterone output may result from the activation of proteolytic events which release aldosterone from a sequestered intraglandular pool. These proteolytic events are mimicked by the addition of trypsin to whole tissue incubations in vitro. Experiments were carried out to determine what factors may govern the size of such intraglandular steroid pools. The most remarkable effect was that prior sodium depletion greatly enhanced the yield (2–3-fold) of aldosterone on subsequent incubation of adrenal capsules with trypsin, to an extent far greater than the increase in basal (non trypsin induced) aldosterone output in this tissue. Although betamethasone (20 μg/ml in drinking water) and the converting enzyme inhibitor captopril (7.2 mg/day) eliminated trypsin releasable steroid in control animals, they had no effect on the enhanced levels of trypsin releasable steroid seen with sodium depletion. The data suggest that trypsin releasable steroid pools are variable in accordance with the physiological requirements of the animal, particularly in sodium depletion.