AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 4 861-R865, Copyright © 1989 by American Physiological Society
Effect of cortisol on vasopressin response to hypertonic saline in fetal sheep
T. L. Bennett and J. C. Rose
Department of Obstetrics and Gynecology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27103.
To determine the effect of cortisol on vasopressin responses to
hyperosmolality, we infused hypertonic saline (HS) (12 meq/kg NaCl) into
nine chronically cannulated fetal sheep ranging from 110 to 132 days of
gestation. The experiment was performed twice on each fetus, once during a
continuous cortisol infusion and once during a vehicle infusion.
Administration of HS resulted in a prompt increase in serum osmolality from
292.1 +/- 1.8 to 310.4 +/- 2.5 mosmol/kg. Decreases were seen in pH,
partial pressure of O2, and hematocrit from 7.37 +/- 0.01 to 7.31 +/- 0.01,
from 22.5 +/- 1.6 to 20.0 +/- 2.0 mmHg, and from 35.6 +/- 1.7 to 32.6 +/-
1.6, respectively. Mean arterial pressure increased from 41.3 +/- 1.4 to
48.9 +/- 2.0 mmHg (P less than 0.01). Arginine vasopressin (AVP) rose from
base line after HS (P = 0.11 vehicle experiments, P = 0.04 cortisol
experiments), and AVP responses were greater in the cortisol experiments
than in the vehicle experiments (delta AVP = 21.9 +/- 10.9 vs. 3.1 +/- 0.9
pg/ml, P = 0.05). Also there was a correlation noted between differences in
AVP response and cortisol levels (P less than 0.04). We conclude that
cortisol exerts a positive influence on the AVP response to HS in fetal
sheep.
