AJP - Endocrinology and Metabolism, Vol 262, Issue 3 E325-E329, Copyright © 1992 by American Physiological Society
ACTH and cortisol responses to hypotension in fetal sheep after a prior CRF injection
D. R. Kerr, M. I. Castro, N. K. Valego, N. M. Rawashdeh and J. C. Rose
Department of Physiology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27103.
To determine whether an ovine corticotropin-releasing factor (oCRF)
injection modifies adrenocorticotropic hormone (ACTH) and cortisol
responses to hypotension and whether the effect of any interactions between
these stimuli changes across gestation, we studied chronically cannulated
fetal lambs of 103-113 ("immature") and 133-139 days gestation ("mature").
Experimental groups received 500 ng/kg oCRF injections and 6 h later had
arterial pressure reduced 20% for 10 min with nitroprusside. Blood samples
were obtained before and after each manipulation. Controls received vehicle
instead of oCRF. The oCRF increased plasma cortisol levels from 2.1 +/- 0.4
to 14.2 +/- 4.7 (SE) ng/ml in immature and 44.9 +/- 2.2 to 102.8 +/- 15
ng/ml in mature animals. In mature fetuses the oCRF did not alter plasma
ACTH and cortisol increases due to hypotension. In immature animals ACTH
increases were normal but cortisol increases were eliminated. This suggests
that the CRF caused maximal stimulation of the adrenal gland. In older
fetuses, it appears that the action of ACTH-releasing factors, secreted in
response to arterial hypotension, can overcome the negative feedback
effects of elevations in endogenous cortisol.
