Effect of human chorionic gonadotropin (hCG) on in vitro oocyte maturation in freshwater cyprinid, <i>Barilius vagra</i>

Abstract

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).