title: The influence of calcium ionophore and activators of protein kinase C on steroid production by preovulatory ovarian follicles of the goldfish.
abstract: Steroidogenesis in teleost fish, as in other vertebrate groups, is mediated by the activation of adenylate cyclase. For the present studies, calcium ionophore A23187 and either phorbol 12-myristate 13-acetate (PMA) or 1-oleoyl-2-acetylglycerol (OAG) were used to investigate the possible roles that changes in intracellular calcium content and protein kinase C activation play in steroid production by goldfish preovulatory ovarian follicles incubated in vitro. While ineffective alone, PMA (1.6-400 nM) and OAG (25-100 micrograms/ml) exhibited classical synergism with A23187 (1.0-10 microM), leading to increased testosterone production. The magnitude of these responses was at least tenfold lower than that obtained with human chorionic gonadotropin (hCG), forskolin, or dibutyryl cyclic adenosine 3',5'-monophosphate. Testosterone production stimulated by hCG and forskolin was blocked by addition of PMA but not OAG. Unlike PMA, the inactive phorbol ester 4 alpha-phorbol 12,13-dideconate did not influence basal or stimulated testosterone production. A23187 had a biphasic effect on stimulated testosterone production: a dosage of 0.25 or 1.0 microM potentiated the action of submaximally effective dosages of hCG or forskolin on testosterone production; a higher dosage of 4 microM inhibited stimulated testosterone production by up to 50%. In conclusion, these studies suggest that, in addition to the adenylate cyclase second messenger system, changes in intracellular calcium and activation of protein kinase C may modulate steroidogenesis in goldfish ovarian follicles.
authors.affiliation: Department of Zoology, University of Guelph, Ontario, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Van der Kraak
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D003530:Cyprinidae / Q000378:metabolism*; D004075:Diglycerides / Q000494:pharmacology*; D005260:Female; D005989:Glycerides / Q000494:pharmacology*; D006054:Goldfish / Q000378:metabolism*; D006080:Ovarian Follicle / Q000187:drug effects / Q000378:metabolism*; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D013739:Testosterone / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D004075:Diglycerides; D005989:Glycerides; D010703:Phorbol Esters; D000001:Calcimycin; D013739:Testosterone; C038237:1-oleoyl-2-acetylglycerol; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium