AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 5 611-R616, Copyright © 1985 by American Physiological Society
Acute volume expansion decreases adrenocortical sensitivity to ACTH and angiotensin II
H. Raff, J. Shinsako, C. E. Wade, L. C. Keil and M. F. Dallman
This study examined the plasma aldosterone and corticosteroid responses to
a 60-min infusion of adrenocorticotropin (ACTH) or angiotensin (ANG) II
started immediately after an acute isotonic saline volume expansion (0.5 ml
. kg-1 . min-1 for 30 min). Five conscious dogs of either sex with
exteriorized carotid loops were used in this repeated-design study. Volume
expansion per se caused a 10% decrease in hematocrit, a 12.5% decrease in
plasma protein, and a 2.7-mmHg increase in central venous pressure with no
change in mean arterial pressure, heart rate, or plasma sodium. Volume
expansion per se also resulted in significant reductions in vasopressin,
plasma renin activity, ACTH, aldosterone, and corticosteroid levels. The
aldosterone responses to ACTH and ANG II were significantly inhibited
(46-71%) by acute volume expansion. The corticosteroid response to ACTH was
19-29% inhibited by volume expansion. We conclude that acute volume
expansion significantly inhibits the adrenocortical sensitivity to its
tropic hormones probably via alterations of synergistic factors.
