The responses of adrenocorticotrophic hormone and cortisol to insulin-induced hypoglycaemic stress in man are unimpaired during chronic converting enzyme inhibition.

In vitro and animal studies indicate that circulating angiotensin II (ANG II) can stimulate adrenocorticotrophic hormone (ACTH) and cortisol secretion, but it is far from established that ANG II has a physiologically relevant influence on steroidogenesis. We studied the effects of hypoglycaemia induced with insulin injection (0.15 IU/kg) in patients with essential hypertension to answer this question. Hypoglycaemia was induced before and after a short term course of treatment with the converting enzyme inhibitor captopril to obtain a sustained blockade of ANG II formation. Alterations in serum glucose, plasma potassium, plasma ACTH, cortisol, renin activity and aldosterone were examined. In control studies there was a profound fall in serum glucose and plasma potassium after insulin, associated with increments in plasma renin activity, which correlated with those of aldosterone but not with those of ACTH and cortisol. Chronic captopril increased baseline plasma renin activity and lowered baseline aldosterone while leaving ACTH and cortisol unchanged. During converting enzyme inhibition the insulin-induced decrements in glucose and potassium, as well as the increments in ACTH, cortisol and aldosterone, were similar to those observed in control studies, whereas the increments in plasma renin activity were much greater. From these results it does not appear that ANG II has a relevant influence on ACTH and cortisol production, or on their responses to hypoglycaemic stress. Rather, these findings indicate that even under the present experimental conditions ANG II is the primary regulator of aldosterone secretion. However, this function can be taken over by ACTH when the generation of ANG II is blocked.