Control of zona glomerulosa function in the isolated perfused rat adrenal gland in situ

Abstract

The extent to which results obtained using in-vitro techniques can be taken to reflect in-vivo physiological responses in the study of adrenocortical function has not been subjected to systematic study. Some evidence suggests that in-vitro preparative methods may affect the secreted steroid profile. For this reason it seemed desirable to study adrenal function using an isolated perfused whole gland technique, and this study reports results obtained with known aldosterone stimulants. Angiotensin II, ACTH and potassium ions all stimulated aldosterone secretion in a dose-dependent manner. The stimulation thresholds of these substances were compatible with their normal circulating concentrations. For angiotensin II stimulation this preparation was two orders of magnitude more sensitive than any in-vitro preparation. Most importantly, the specific glomerulosa effectors, angiotensin II and potassium, selectively stimulated aldosterone output, and had no consistent effect on corticosterone secretion at any dose used. On the other hand, ACTH stimulated both corticosterone and aldosterone output at all effective concentrations. The actions of α-MSH were also studied using this preparation. Low doses of α-MSH selectively stimulated aldosterone secretion, while higher doses were needed to stimulate corticosterone. The onset of response to all stimulants was invariably seen within the first 10 min after administration of stimulants. Maximal aldosterone output was achieved within the first 10 min whereas corticosterone secretion usually peaked 10–20 min later. The amount of aldosterone produced by this preparation was much higher than the amount produced by dispersed cell preparations, and closely approximated to the levels of aldosterone obtained in adrenal vein blood. The data indicate that the isolated circulation perfused gland system is a sensitive preparation which approximates to the physiological condition. In particular, aldosterone is the prominent glomerulosa product, and corticosterone is, in this system, a more specific marker for inner zone function. J. Endocr. (1985) 104, 387–395