Site of calcium requirement for stimulation of ACTH release in rat anterior pituitary cells in culture by synthetic ovine corticotropin-releasing factor |
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Authors: | V Giguere G Lefevre F Labrie |
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Institution: | MRC Group in Molecular Endocrinology, Le Centre Hospitalier de l''Université Laval, Quebec G1V 4G2, Canada |
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Abstract: | Synthetic ovine corticotropin-releasing factor (CRF) causes a 6- to 8-fold stimulation of ACTH release and cAMP accumulation in rat anterior pituitary cells in culture at ED50 values of 1 and 4 nM, respectively. Removal of Ca2+ from the incubation medium reduces CRF-induced ACTH release by 70% but have no effect on cyclic AMP accumulation. ACTH release induced by 8-Br-cAMP is inhibited by 65% in the absence of Ca2+. The Ca2+ ionophore A23187 does not alter spontaneous ACTH release. Verapamil, a pharmacological agent that blocks Ca2+ entry into cells, has no influence on spontaneous or CRF-induced ACTH release. The present data clearly demonstrate a role of Ca2+ in CRF action at a step subsequent to cAMP formation and suggest that Ca2+ is mobilized from intracellular stores during CRF stimulation. |
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