title: Cortisol rapidly reduces prolactin release and cAMP and 45Ca2+ accumulation in the cichlid fish pituitary in vitro.
abstract: During in vitro incubation, prolactin release is inhibited in a dose-related manner by cortisol. This action is mimicked by the synthetic glucocorticoid agonist dexamethasone but not by other steroids tested. Perifusion studies indicate that the inhibition of [3H]prolactin release by cortisol occurs within 20 min. Cortisol (50 nM) also inhibits cAMP accumulation and reduces 45Ca2+ accumulation in the tilapia rostral pars distalis within 15 min. Cortisol's action on prolactin release is blocked in the presence of either the Ca2+ ionophore A23187 or a combination of dibutyryl cAMP and 3-isobutyl-1-methylxanthine, which increase intracellular Ca2+ and cAMP, respectively. Taken together, these findings suggest that cortisol may play a physiologically relevant role in the rapid modulation of prolactin secretion in vivo. Our studies also suggest that the inhibition of prolactin release by cortisol is a specific glucocorticoid action that may be mediated, in part, through cortisol's ability to inhibit intracellular cAMP and Ca2+ metabolism.
authors.affiliation: Department of Zoology and the Hawaii Institute of Marine Biology, University of Hawaii, Honolulu, HI 96822, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Borski
authors.forename: L M
authors.initials: LM
authors.lastname: Helms
authors.forename: N H
authors.initials: NH
authors.lastname: Richman
authors.forename: E G
authors.initials: EG
authors.lastname: Grau