The Effect of β-Adrenergic Blockade on the Release of ACTH and Cortisol In Vivo

Summary

The effect of α-adrenergic blockade, by phentolamine, upon plasma levels of adrenocorticotrophic hormone (ACTH) and cortisol during insulin-induced hypoglycaemia was studied in pigs. Insulin administration produced a rise in ACTH which reached a maximum at about 30 minutes (p< 0.01} and had returned to basal levels by 90 minutes. Cortisol levels had also risen by 30 minutes and remained elevated for 90 minutes.

Pre-treatment with phentolamine almost completely suppressed the growth hormone response to insulin-induced hypoglycaemia, but had no effect upon the amplitude or duration of the elevation of plasma ACTH or cortisol levels following insulin administration. The hypoglycaemia-induced rise in ACTH and cortisol seem, therefore, to be independent of the α-adrenergic system. In addition, the inhibitory action of the α-adrenergic system on ACTH release reported in rats and dogs does not appear to be present in pigs.

Key-Words:

ACTH - Cortisol - Growth Hormone - Hypoglycaemia - Adrenergic System - Pigs