In vitro hormone induction of final oocyte maturation in striped bass (Morone saxatilis) follicles is inhibited by blockers of phosphatidylinositol 3-kinase activity.
Oocyte germinal vesicle breakdown (GVBD) was induced in striped bass ovarian fragments when tissues were incubated with 100-nM recombinant human insulin-like growth factor-I (rhIGF-I), 25-IU human chorionic gonadotropin (hCG) ml(-1), or 290 nM of the maturation-inducing steroid (MIS), 17,20beta,21-trihydroxy-4-pregnen-3-one (20beta-S). Inhibitors of phosphatidylinositol 3-kinase (PI 3-K), wortmannin (100 nM) and LY 294002 (50 microM), inhibited GVBD induced by these hormones. Furthermore, the inhibitors attenuated hCG-induced steroid hormone synthesis. Previous studies report that gap junction uncouplers inhibit GVBD induced by hCG, but not by rhIGF-I, in striped bass. We show that 20beta-S-induced GVBD is also attenuated by 1 mM 1-heptanol or 1-octanol without being affected by incubation with 3 mM ethanol. Thus, the effects of inhibiting PI 3-K activity on GtH and MIS actions are similar to effects of uncoupling gap junctions. These data suggest that PI 3-K activity is required for GtH- MIS- and IGF-I induction of GVBD in striped bass. Our data are also consistent with the notion that a ligand that regulates PI 3-K activity, possibly an IGF, participates in maintenance of gap junctional communication required for maximal GtH and MIS action.
Weber
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GM
Department of Zoology, North Carolina State University, Campus Box 7617, Raleigh, NC 27695-7617, USA. weber@unity.ncsu.edu
Sullivan
C V
CV
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001492:Bass / Q000502:physiology*; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D017629:Gap Junctions / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin
D000730:Androstadienes; D006063:Chorionic Gonadotropin; D002867:Chromones; D004791:Enzyme Inhibitors; D007334:Insulin-Like Growth Factor I; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one