Acute volume expansion significantly inhibited the aldosterone responses to ACTH and ANG II by 46-71% and the corticosteroid response to ACTH by 19-29%.
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.
Raff et al. (1985) studied this question. Acute isotonic saline volume expansion was evaluated on Plasma aldosterone and corticosteroid responses to ACTH or ANG II. Acute volume expansion significantly inhibited the aldosterone responses to ACTH and ANG II by 46-71% and the corticosteroid response to ACTH by 19-29%.
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