AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 2 339-R347, Copyright © 1989 by American Physiological Society
Vasopressin and ANG II in the control of ACTH secretion and arterial and atrial pressures
V. L. Brooks
Department of Physiology, Oregon Health Sciences University, Portland 97201.
Hypotension stimulates the secretion of adrenocorticotropin (ACTH) and
vasopressin (AVP) and increases plasma levels of angiotensin II (ANG II).
Because AVP and ANG II increase ACTH secretion, the present experiments
were performed to evaluate the role of these peptides in the increases in
plasma ACTH and glucocorticoid concentrations produced by hypotension in
conscious dogs. This was accomplished by determining whether administration
of receptor antagonists to vasopressin,
[1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),
2-(O-methyl)tyrosine]Arg8-vasopressin, and ANG II (saralasin), reduced the
ACTH and glucocorticoid responses to infusion of four doses of the
vasodilator nitroprusside. Nitroprusside (NP) infusion produced
dose-dependent decreases in mean arterial pressure. Larger decreases in
arterial pressure were produced in dogs pretreated with the AVP antagonist
or with both saralasin and the vasopressin antagonist. Left and right
atrial pressures also fell with NP infusion, and larger decreases in atrial
pressures were found in dogs pretreated with the AVP antagonist. Finally,
NP infusion increased plasma glucocorticoid concentration and plasma ACTH
concentration. Both the glucocorticoid and the ACTH responses to
hypotension were reduced in dogs given the AVP antagonist and in dogs given
both saralasin and the AVP antagonist, but there was no difference in the
effect of AVP blockade alone vs. the effect of combined AVP and ANG II
blockade. These data suggest that AVP, but not ANG II, is required for
normal glucocorticoid and ACTH responses to hypotension. They also suggest
that AVP is necessary for normal maintenance of arterial blood pressure and
atrial pressures during NP infusion.
