title: In vitro steroid-induced meiosis in Rhinella arenarum oocytes: role of pre-MPF activation.
abstract: In this work we showed the relationship between seasonal periods and the response of R. arenarum follicles and oocytes to different steroids. Using in vitro germinal vesicle breakdown (GVBD) assays, we demonstrated that P4 is the main steroid capable of inducing maturation in R. arenarum oocytes and follicles. In the second part of this work we showed that androgens can activate pre-maturation promoting factors (pre-MPFs) such as P4, by cytoplasm microinjection experiments. The results indicated that the steroids assayed induced oocyte and follicle maturation in a dose- and time-dependent manner. In oocytes, P4 was the most efficient steroid as a maturation inducer (EC50 of the reproductive period, 6 nM, EC50 of the non-reproductive period ≅ 30 nM). Androgens (DHEA, dehydroepiandrosterone; T, testosterone; and AD, androstenedione) were less efficient maturation inducers than P4 (EC50 reproductive period ≅ 50, 120 and 600 nM respectively). Similar results were obtained with intact follicles in both seasonal periods. Although the response of follicles to the different androgens was variable, in no case was it above the above the response induced by P4. Independently of the season, oocytes and follicles incubated in P4, P5 and T underwent GVBD after 6-10 h while oocytes and follicles incubated in DHEA and AD matured more slowly. Furthermore, we demonstrated that microinjection of mature cytoplasm from androgen-treated oocytes is sufficient to promote GVBD in immature recipient oocytes (DHEA, 57 ± 12%; AD, 60 ± 8%; T, 56 ± 13%). Thus, androgens such as DHEA, T and AD are as competent as P4 to activate pre-MPF.
authors.affiliation: Instituto de Biología,Facultad de Bioqca,Qca. y Farmacia,INSIBIO-UNT,Chacabuco 461,Tucumán,Argentina.
authors.forename: Ana Josefina
authors.initials: AJ
authors.lastname: Arias Torres
authors.affiliation: Instituto de Biología,Facultad de Bioqca,Qca. y Farmacia,INSIBIO-UNT,Chacabuco 461,Tucumán,Argentina.
authors.forename: Marta Inés
authors.initials: MI
authors.lastname: Bühler
authors.affiliation: Instituto de Biología,Facultad de Bioqca,Qca. y Farmacia,INSIBIO-UNT,Chacabuco 461,4000 San Miguel de Tucumán,Tucumán,Argentina.
authors.forename: Liliana Isabel
authors.initials: LI
authors.lastname: Zelarayán
mesh_terms: D000728:Androgens / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D002022:Bufo arenarum; D002478:Cells, Cultured; D003593:Cytoplasm / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D012739:Gonadal Steroid Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods; D016200:Maturation-Promoting Factor / Q000378:metabolism*; D008540:Meiosis / Q000187:drug effects*; D008845:Microinjections; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009866:Oogenesis / Q000187:drug effects; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology; D011498:Protein Precursors / Q000378:metabolism*; D012621:Seasons; D013739:Testosterone / Q000008:administration & dosage / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000728:Androgens; D012739:Gonadal Steroid Hormones; D011498:Protein Precursors; C067034:maturation-promoting factor precursor; D013739:Testosterone; D011374:Progesterone; D016200:Maturation-Promoting Factor
keywords: MPF; Oocyte maturation; Rhinella arenarum; Seasonal changes; Steroids