Effect of adrenocorticotrophic hormone on the in vivo output of adenosine 3'5' cyclic monophosphate and corticosteroids by the sheep adrenal gland

Abstract

The effect of intravenous infusion of adrenocorticotrophic hormone (ACTH) (12u/h) on the adrenal venous concentration of adenosine 3'5' cyclic monophosphate (c-AMP) was studied in five conscious sheep with a cervical adrenal autotransplant. In addition adrenal vein blood was assayed for cortisol, corticosterone and aldosterone. ACTH infusion caused a rapid increase in adrenal c-AMP output which was apparent within the first minute of infusion and which appeared to precede the increase in steroid production. Peak c-AMP output was 10–100 fold greater than pre-infusion output and was reached within 15 min of infusion. Maximum steroid production also occurred at about 15 min. However, in contrast to adrenal steroid production, the increase in adrenal c-AMP output was not sustained at the maximum rate and decreased gradually during the infusion period. In sheep with maximum pre-infusion steroid production, adrenal c-AMP output was increased by ACTH infusion. The basal c-AMP concentration in arterial plasma was 10–35 nM and no significant increase was observed during ACTH infusion. The response pattern of c-AMP and steroid secretion by the adrenal gland in vivo to a large dose of ACTH confirms that previously reported from in vitro studies.