A Comparative study of synthetic carp GnRH and carp pituitary homogenate effects on in vitro steroidogenesis of oocytes in common carp (Cyprinus carpio)

Vitellogenic stage carp ovaries were collected aseptically and the cells of ovarian follicles were dispersed by trypsin treatment and cultivated as monolayer. Control cultures were grown in medium M199 alone. Media for experimental cultures were supplemented either with 100 µl ml-1 of CPH and CPS-carp GnRH (cultivated pituitary cell secretion affected by 10-6, 10-8, 10-10 M carp GnRH). The direct effect of these factors on 17-α-Hydroxy progesterone (17α -OHP) and 17β-Estradiol (E2) secretion of isolated follicular cells in cell culture was assayed by appropriate Radioimmunoassay (RIA). According to the results the E2 was a main hormone secreted by cultivated carp granulosa and theca cells. Adding 100 µl ml-1of 10-6 M CPS-carp GnRH had no significant effect on cultivated granulosa and theca cells endocrine activity (P> 0.05). On the other hand, carp granulosa and theca cells treated with the lower contents of CPS-carp GnRH (10-8, 10 -10 M) showed a 4.02 and 3.74-fold increase in E2 concentration and 4.27 and 3.64-fold increase in 17α -OHP level, which was significantly higher than CPH (P< 0.05). Also, there was a significant increase of steroid secretion in group stimulated with 100 µl ml-1 of CPS and CPH, but there were no significant differences between them (P> 0.05).