Adrenal blood flow and the adrenocortical response to corticotropin

Abstract

The effect of variations in adrenal blood flow on the adrenocortical response to ACTH was studied. The rate of blood flow through the perfused canine adrenal gland was a significant parameter in its response to ACTH. This effect was largest when the concentration of ACTH was between 1 and 30 µU/ml blood, but was considerably reduced in magnitude or absent at higher ACTH concentrations or in the absence of ACTH. The results at a variety of blood flows and blood ACTH concentrations indicate that the rate of ACTH presentation to the adrenal gland was better correlated with the steady-state rate of cortisol secretion than was blood ACTH concentration. The time course of adrenocortical response to a twofold increase in blood flow at an ACTH concentration of 1 µU/ml corresponded to dynamic responses to an increase in ACTH concentration at constant flow. Adrenal blood flow is approximately linearly related to perfusion pressure. It is concluded that adrenocortical function is an equivocal index of ACTH release by the pituitary, unless adrenocortical blood flow is known to be constant.