Acute volume expansion decreases adrenocortical sensitivity to ACTH and angiotensin II
Raff, H.; Shinsako, J.; Wade, C.E.; Keil, L.C.; Dallman, M.F.
American Journal of Physiology 249(5 Pt 2): R611-R616
1985
ISSN/ISBN: 0002-9513 PMID: 2998212 Document Number: 244451
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 .cntdot. kg-1 .cntdot. 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-mm Hg 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.