AJP - Endocrinology and Metabolism, Vol 268, Issue 1 E85-E91, Copyright © 1995 by American Physiological Society
Evidence for a single glucocorticoid regulated pool of adrenocorticotropin in sheep anterior pituitary
R. J. Kemppainen and T. P. Clark
Department of Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Alabama 36849.
The goal of this study was to determine whether separate
glucocorticoid-sensitive releasable pools of adrenocorticotropic hormone
(ACTH) could be distinguished in sheep anterior pituitary cells. Isolated
cells were cultured in serum-free medium containing 0-10 nM cortisol (F)
for 7-11 days to determine whether variation in the glucocorticoid
environment selectively affected ACTH release stimulated by
corticotropin-releasing hormone (CRH) or arginine vasopressin (AVP).
Secretion was studied using a microperifusion system. The results indicated
that while the concentration of F in the medium bathing the cells
profoundly influenced the magnitude of ACTH released in response to either
peptide, the fractional release of total ACTH was unchanged. F
concentration in culture medium similarly did not alter the
negative-feedback effectiveness of a larger dose of F applied to cells 45
min before treatment with CRH or AVP. These results support the existence
of a single glucocorticoid-sensitive pool of ACTH in corticotrophs.
