title: Regulation of recombinant human insulin-induced maturational events in Clarias batrachus (L.) oocytes in vitro.
abstract: Regulation of insulin-mediated resumption of meiotic maturation in catfish oocytes was investigated. Insulin stimulation of post-vitellogenic oocytes promotes the synthesis of cyclin B, histone H1 kinase activation and a germinal vesicle breakdown (GVBD) response in a dose-dependent and duration-dependent manner. The PI3K inhibitor wortmannin abrogates recombinant human (rh)-insulin action on histone H1 kinase activation and meiotic G2-M1 transition in denuded and follicle-enclosed oocytes in vitro. While the translational inhibitor cycloheximide attenuates rh-insulin action, priming with transcriptional blocker actinomycin D prevents insulin-stimulated maturational response appreciably, albeit in low amounts. Compared with rh-insulin, human chorionic gonadotrophin (hCG) stimulation of follicle-enclosed oocytes in vitro triggers a sharp increase in 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DHP) secreted in the incubation medium at 12 h. Interestingly, the insulin, but not the hCG-induced, maturational response shows less susceptibility to steroidogenesis inhibitors, trilostane or dl-aminoglutethimide. In addition, priming with phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) or cell-permeable dbcAMP or adenylyl cyclase activator forskolin reverses the action of insulin on meiotic G2-M1 transition. Conversely, the adenylyl cyclase inhibitor, SQ 22536, or PKA inhibitor H89 promotes the resumption of meiosis alone and further potentiates the GVBD response in the presence of rh-insulin. Furthermore, insulin-mediated meiotic maturation involves the down-regulation of endogenous protein kinase A (PKA) activity in a manner sensitive to PI3K activation, suggesting potential involvement of a cross-talk between cAMP/PKA and insulin-mediated signalling cascade in catfish oocytes in vitro. Taken together, these results suggest that rh-insulin regulation of the maturational response in C. batrachus oocytes involves down-regulation of PKA, synthesis of cyclin B, and histone H1 kinase activation and demonstrates reduced sensitivity to steroidogenesis and transcriptional inhibition.
authors.affiliation: Department of Zoology,Visva-Bharati University,Santiniketan-731235,India.
authors.forename: Sudip
authors.initials: S
authors.lastname: Hajra
authors.affiliation: Department of Zoology,Visva-Bharati University,Santiniketan-731235,India.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Das
authors.affiliation: Department of Zoology,Visva-Bharati University,Santiniketan-731235,India.
authors.forename: Pritha
authors.initials: P
authors.lastname: Ghosh
authors.affiliation: Department of Zoology,Visva-Bharati University,Santiniketan-731235,India.
authors.forename: Soumojit
authors.initials: S
authors.lastname: Pal
authors.affiliation: Department of Zoology,Visva-Bharati University,Santiniketan-731235,India.
authors.forename: Poulomi
authors.initials: P
authors.lastname: Nath
authors.affiliation: Department of Zoology,Visva-Bharati University,Santiniketan 731235,India.
authors.forename: Sudipta
authors.initials: S
authors.lastname: Maitra
mesh_terms: D000818:Animals; D002397:Catfishes; D002453:Cell Cycle / Q000187:drug effects*; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006908:Hydroxyprogesterones / Q000378:metabolism; D015151:Immunoblotting; D007328:Insulin / Q000235:genetics / Q000494:pharmacology*; D008540:Meiosis / Q000187:drug effects*; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D006080:Ovarian Follicle / Q000166:cytology; D011494:Protein Kinases / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors
chemical_list: D006063:Chorionic Gonadotropin; D019926:Cyclin B; D006908:Hydroxyprogesterones; D007328:Insulin; D011500:Protein Synthesis Inhibitors; D011994:Recombinant Proteins; C007433:17,20-dihydroxy-4-pregnen-3-one; D003609:Dactinomycin; D003513:Cycloheximide; D011494:Protein Kinases; C102333:histone H1 kinase; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: Catfish; Insulin; Oocyte; Ovarian follicles; PI3K; cAMP/PKA