AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 6 1193-R1199, Copyright © 1986 by American Physiological Society
Adrenal medullary responses to repeated hemorrhage in conscious dogs
M. P. Lilly, W. C. Engeland and D. S. Gann
Potentiated adrenal responses to the second of two identical hemorrhages
spaced 24 h apart are seen in the pentobarbital sodium-anesthetized dog.
Although pentobarbital effectively reduces environmental influences,
barbiturates affect hemodynamic and hormonal responses and preclude normal
daily feeding and activity patterns. To determine the role of anesthesia in
these earlier results, we prepared awake trained dogs with chronic adrenal
venous catheters. Animals were bled 8.7-21.8% of measured blood volume
[131] over 3 min, and peripheral and adrenal blood was sampled. Blood was
reinfused 1 h later, and the dogs were fed. The protocol was repeated 24 h
later. Dogs with small hemorrhage (11.6 +/- 2.3% blood vol; n = 9) showed
no difference in catecholamine secretion on the 2 days. Dogs with large
hemorrhage (18.9 +/- 2.1% blood vol; n = 9) showed a greater epinephrine
and norepinephrine secretory response to hemorrhage on day 2. No
differences were detected in the hemodynamic response to bleeding on the 2
days. Whereas potentiation was seen in epinephrine and norepinephrine
responses to a second 10% hemorrhage in anesthetized dogs, larger
hemorrhage was needed to elicit this effect in awake dogs. Thus potential
adrenal medullary responses to repeated hemorrhage occur in both awake and
pentobarbital-anesthetized dogs, but important differences in the threshold
and manifestation of this effect are seen.
