Effect of human chorionic gonadotropin (hCG) on in vitro oocyte maturation in freshwater cyprinid, Barilius vagra
In vitro exposure of Barilius vagra ovarian follicles to human chorionic gonadotropin (hCG) influenced the position of germinal vesicle and resulted in a maturation of oocyte, although the response was time dependent. There was slight but significant (P<0.05) increased in germinal vesicle breakdown (GVBD, 12.42 vs. 2.94%) at 24 h, whereas there was significant (P<0.0001) decreased in oocyte having central germinal vesicle (CGV, 59.6 vs. 85%). Prolonged incubation further increased GVBD (29.8% at 72 h) and decreased central position germinal vesicle (CGV, 8.7%). Moreover, hCG treatment at 72 h enhanced the synthesizing capability of the vitellogenic oocytes. There was significant increase in the secretion of estradiol- 17ß (P = 0.0001) and non significant effect on the secretion of testosterone (P = 0.07). 17α- hydroxyprogesterone (17-OHP: 17α-hydroxypregn-4-ene-3, 20-dione) and 17α-20β-dihydroxypregn-4-ene- 3-dione (17,20βP: 17, 20β-dihydroxypregn-4-ene-3-one) were detected and identified only in the hCG treated incubation medium.
Key words: hCG, in vitro, oocyte maturation, germinal vesicle breakdown, maturation inducing steroid (MIS).