Effects of insulin-like growth factor-I on in vitro final oocyte maturation and ovarian steroidogenesis in striped bass, Morone saxatilis.
Recombinant human (rh) insulin-like growth factor-I (IGF-I) was more potent than rhIGF-II at inducing in vitro germinal vesicle breakdown (GVBD), a marker for resumption of meiosis, in oocytes of striped bass. Treatment of ovarian fragments containing oocytes in intact follicles with rhIGF-I increased concentrations of estradiol-17beta and maturation-inducing steroid (MIS) 17,20beta, 21-trihydoxy-4-pregnen-3-one (20beta-S) in the culture medium and decreased testosterone levels. The follicles were too immature for oocytes to complete GVBD in response to 20beta-S (MIS incompetent) or hCG. Addition of 20beta-S to cultures did not increase the percentage of oocytes completing GVBD in response to rhIGF-I or rhIGF-II. Bovine insulin was without effect on GVBD or steroid production. Incubation of MIS-competent follicles with actinomycin D, cyanoketone, trilostane, 1-heptanol, or 1-octanol had no effect on rhIGF-I-induced GVBD, but attenuated hCG-induced GVBD and 20beta-S production. Cycloheximide inhibited rhIGF-I-induced GVBD. Collectively, these observations indicate that IGF-I can induce GVBD via MIS- and transcription-independent pathways without coupled gap junctions between oocytes and granulosa cells or among granulosa cells, but requires protein synthesis to do so. An rhIGF-I analogue that does not bind IGF-binding proteins, des(1,3)IGF-I, was more potent than rhIGF-I in inducing GVBD, suggesting ovarian IGF-binding proteins may inhibit IGF-I action.
Weber
G M
GM
Department of Zoology, North Carolina State University, Raleigh, North Carolina 27695-7617, USA. weber@unity.ncsu.edu
Sullivan
C V
CV
D020003:1-Octanol / Q000494:pharmacology; D000818:Animals; D001492:Bass; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D003350:Cortodoxone / Q000031:analogs & derivatives / Q000378:metabolism; D003489:Cyanoketone / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D019850:Heptanol / Q000494:pharmacology; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D013256:Steroids / Q000378:metabolism*; D022161:Transport Vesicles / Q000187:drug effects; D014475:Uncoupling Agents / Q000494:pharmacology
D006063:Chorionic Gonadotropin; D007328:Insulin; D010446:Peptide Fragments; D011994:Recombinant Proteins; D013256:Steroids; D014475:Uncoupling Agents; D013196:Dihydrotestosterone; C058957:insulin-like growth factor 1, des-(1-3)-; D003609:Dactinomycin; D003489:Cyanoketone; C051954:17,20,21-trihydroxy-4-pregnen-3-one; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D019850:Heptanol; D003513:Cycloheximide; D006913:Hydroxysteroid Dehydrogenases; C009954:trilostane; D020003:1-Octanol; D003350:Cortodoxone