AJP - Endocrinology and Metabolism, Vol 269, Issue 1 E53-E60, Copyright © 1995 by American Physiological Society
Responses of immunoreactive ACTH and bioactive ACTH to large hemorrhage and resuscitation in conscious dogs
M. P. Lilly, G. J. Gala, B. E. Sutherland and D. S. Gann
Department of Surgery, School of Medicine, University of Maryland at Baltimore 21201, USA.
We studied the effect of fluid resuscitation on immunoreactive
adrenocorticotropic hormone (irACTH) and bioactive ACTH (bioACTH) after
hemorrhage in conscious dogs. Animals (n = 7) were bled 30% (approximately
25 ml/kg) over 3 min and 30 min later were either resuscitated [43.3 ml/kg
0.9% NaCl (1.8 times hemorrhage volume) over 10 min] or not. Blood was
reinfused after 210 min. Animals had both treatments (> 4 days apart).
irACTH, bioACTH, cortisol, angiotensin II, and aldosterone increased
rapidly after hemorrhage. Resuscitation increased blood volume and cardiac
output to resting values, but arterial hypotension persisted. bioACTH and
irACTH decreased 40-90 min after hemorrhage in both groups, but each
decreased more rapidly after resuscitation. The elimination half-life of
bioACTH was shorter than that of irACTH, but neither was affected by
resuscitation. The ratio of bioACTH to irACTH followed the same pattern
with or without resuscitation. Angiotensin II and aldosterone remained
increased without resuscitation but decreased promptly after resuscitation.
In conclusion, 1) saline infusion at 1.8 x hemorrhage volume provides
effective cardiovascular resuscitation, with resolution of hormonal
responses to hemorrhage; 2) although ACTH responses resolved with or
without resuscitation, resuscitation produced more rapid resolution without
changing the parameters of ACTH elimination; 3) the dynamics of the
resolution of the ACTH response to hemorrhage are similar whether induced
by stimulus removal or feedback inhibition.
