In vitro effects of insulin-like growth factors and insulin on oocyte maturation and maturation-inducing steroid production in ovarian follicles of common carp, Cyprinus carpio.
In vitro germinal vesicle breakdown (GVBD) in Cyprinus carpio oocytes was induced by recombinant human insulin-like growth factor-I and -II (IGF-I and IGF-II) and bovine insulin (b-insulin). Treatment of postvitellogenic ovarian follicles with IGF-I and b-insulin increased concentration of maturation-inducing hormone (MIH), 17alpha,20beta-dihydroxy-4-pregnane-3-one (DHP) in the medium. IGF-I and IGF-II both and b-insulin induced GVBD in denuded oocytes. IGF-I analogue R3 IGF-I was more potent than IGF-I in inducing GVBD of postvitellogenic follicles suggesting that ovarian IGF binding proteins may inhibit IGF-I action. Vitellogenic follicles, which were immature for oocytes to complete GVBD in response to DHP or HCG, underwent GVBD by IGF-I, not by b-insulin. IGF-I was also able to stimulate DHP production in such follicles. Addition of DHP and HCG to the culture of vitellogenic follicles containing IGF-I or b-insulin did neither potentiate the stimulation of GVBD induced by IGF-I nor initiate the same in response to b-insulin. Incubation of postvitellogenic follicles with trilostane (3beta-HSD inhibitor) had no inhibitory effects on IGF-I- and b-insulin-induced GVBD but attenuated the same under HCG stimulation. Trilostane, however, strongly inhibited DHP production induced by all these effectors. Induction of GVBD by IGF-I and b-insulin was not altered in the presence of actinomycin D. However, it significantly blocked the HCG-induced GVBD. Cycloheximide was shown to inhibit the induction of GVBD and DHP production by IGF-I, b-insulin and HCG. Both actinomycin D and cycloheximide were found to inhibit DHP production stimulated by all the three effectors. Collectively, these observations indicate that IGF-I and b-insulin can induce GVBD via MIH- and transcription-independent pathway. Incubation of the follicles with gap junction uncouplers, 1-heptanol or 1-octanol, had no effect on IGF-I- and b-insulin-induced GVBD, but attenuated the same induced by HCG. These uncouplers, however, inhibited DHP production induced by IGF-I, b-insulin and HCG. This result suggests that both IGF-I and b-insulin can induce oocyte maturation without coupled gap junction between oocytes and granulosa cells, while homologous gap junctions are required for DHP production. Inhibitors of phosphatidylinositol-3 kinase (PI-3 kinase), wortmannin and LY294002 inhibited GVBD by IGF-I and b-insulin. These two inhibitors also attenuated HCG-induced GVBD. These data suggest that PI-3 kinase activity is required for IGF-I, b-insulin and HCG induction of GVBD in C. carpio.
Endocrinology Laboratory, Department of Zoology, University of Kalyani, Kalyani-741235, West Bengal, India. dilipmukher@rediffmail.com
Dilip
D
Mukherjee
Dola
D
Mukherjee
Utpal
U
Sen
Sudipta
S
Paul
S P
SP
Bhattacharyya
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002347:Carps / Q000378:metabolism*; D002417:Cattle; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D006801:Humans; D006908:Hydroxyprogesterones / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013002:Somatomedins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013045:Species Specificity; D013256:Steroids / Q000096:biosynthesis*; D013997:Time Factors; D000077191:Wortmannin
D000730:Androstadienes; D006063:Chorionic Gonadotropin; D002867:Chromones; D006908:Hydroxyprogesterones; D007328:Insulin; D009025:Morpholines; D013002:Somatomedins; D013256:Steroids; D013196:Dihydrotestosterone; C007433:17,20-dihydroxy-4-pregnen-3-one; D003609:Dactinomycin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D003513:Cycloheximide; C009954:trilostane; D000077191:Wortmannin