RESUMO
In this work, we describe the validation of an electrochemiluminescence immunoassay (ECLIA) that allowed us for the first time to determine the levels of progesterone (P4 ) and testosterone (T) secreted by Rhinella arenarum follicles during the preovulatory (POP) and reproductive (RP) periods. We also verified the relation between P4 and T levels and oocyte maturation. Moreover, we demonstrated that the extraction protocol developed for the determinations of P4 and T by ECLIA proved to be efficient and reproducible since the efficacy of the extraction was above 95% in all assays conducted. The results indicate that in the validation process the variation coefficient (CV) between assays is compatible with the analytical procedures based on automated immunoassays (CV < 8%) and that the adaptation proposed for the samples allows the determination of T and P4 with the Cobas e-411 analyzer. Our results indicate that in basal conditions the levels of T released by R. arenarum follicles were higher than those of P4 during POP and RP. In these conditions, steroid secretion failed to induce germinal vesicle break down (GVBD) in the follicles. Under gonadotropin stimulation, steroidogenesis showed a remarkable increase in both periods, especially during POP. This increase was correlated with a high maturation percentage in the follicles incubated in vitro (GVBD = 72 ± 16%) during POP. During RP, human Chorionic Gonadotropin (hCG) induced 81.75 ± 9.1% GVBD. This study is the first report of the seasonal steroidogenic activity in the ovary of R. arenarum in situ using an ECLIA-modified protocol developed in our laboratory.
Assuntos
Bufo arenarum/metabolismo , Imunoensaio/métodos , Ovário/metabolismo , Progesterona/análise , Testosterona/análise , Animais , Bufo arenarum/fisiologia , Feminino , Luminescência , Oogênese , Ovário/fisiologia , Progesterona/isolamento & purificação , Testosterona/isolamento & purificaçãoRESUMO
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 â 30 nM). Androgens (DHEA, dehydroepiandrosterone; T, testosterone; and AD, androstenedione) were less efficient maturation inducers than P4 (EC50 reproductive period â 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.
Assuntos
Hormônios Esteroides Gonadais/farmacologia , Fator Promotor de Maturação/metabolismo , Meiose/efeitos dos fármacos , Oócitos/efeitos dos fármacos , Precursores de Proteínas/metabolismo , Androgênios/administração & dosagem , Androgênios/farmacologia , Animais , Bufo arenarum , Células Cultivadas , Citoplasma/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ativação Enzimática/efeitos dos fármacos , Feminino , Hormônios Esteroides Gonadais/administração & dosagem , Técnicas de Maturação in Vitro de Oócitos/métodos , Microinjeções , Oócitos/citologia , Oócitos/fisiologia , Oogênese/efeitos dos fármacos , Folículo Ovariano/citologia , Folículo Ovariano/efeitos dos fármacos , Folículo Ovariano/fisiologia , Progesterona/administração & dosagem , Progesterona/farmacologia , Estações do Ano , Testosterona/administração & dosagem , Testosterona/farmacologia , Fatores de TempoRESUMO
There are no studies that document the production of prostaglandins (PGs) or their role in Rhinella arenarum oocyte maturation. In this study, we analysed the effect of arachidonic acid (AA) and prostaglandins (PGs) on maturation, activation and pronuclear formation in R. arenarum oocytes. Our results demonstrated that AA was capable of inducing maturation in time-dependent and dose-dependent manner. Arachidonic acid-induced maturation was inhibited by indomethacin. PGs from AA hydrolysis, such as prostaglandin F2α (PGF2α) and, to a lesser extent, PGE2, induced meiosis resumption. Oocyte maturation in response to PGF2α was similar to that produced by progesterone (P4). Oocyte response to PGE1 was scarce. Rhinella arenarum oocyte PGF2α-induced maturation showed seasonal variation. From February to June, oocytes presented low sensitivity to PGF2α. In following periods, this response increased until a maximum was reached during October to January, a close temporal correlation with oocyte response to P4 being observed. The effect of PGF2α on maturation was verified by analysing the capacity of oocytes to activate and form pronuclei after being injected with homologous sperm. The cytological analysis of activated oocytes demonstrated the absence of cortical granules in oocytes, suggesting that PGF2α induces germinal vesicle breakdown (GVBD) and meiosis resumption up to metaphase II. In turn, oocytes matured by the action of PGF2α were able to form pronuclei after fertilization in a similar way to oocyte maturated by P4. In microinjection of mature cytoplasm experiments, the transformation of pre-maturation promoting factor (pre-MPF) to MPF was observed when oocytes were treated with PGF2α. In summary, our results illustrated the participation of the AA cascade and its metabolites in maturation, activation and pronuclei formation in R. arenarum.