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 M۱۹۹ alone. Media for experimental cultures were supplemented either with ۱۰۰ µl ml-۱ of CPH and CPS-carp GnRH (cultivated pituitary cell secretion affected by ۱۰-۶, ۱۰-۸, ۱۰-۱۰ M carp GnRH). The direct effect of these factors on ۱۷-α-Hydroxy progesterone (۱۷α -OHP) and ۱۷β-Estradiol (E۲) secretion of isolated follicular cells in cell culture was assayed by appropriate Radioimmunoassay (RIA). According to the results the E۲ was a main hormone secreted by cultivated carp granulosa and theca cells. Adding ۱۰۰ µl ml-۱of ۱۰-۶ M CPS-carp GnRH had no significant effect on cultivated granulosa and theca cells endocrine activity (P> ۰.۰۵). On the other hand, carp granulosa and theca cells treated with the lower contents of CPS-carp GnRH (۱۰-۸, ۱۰ -۱۰ M) showed a ۴.۰۲ and ۳.۷۴-fold increase in E۲ concentration and ۴.۲۷ and ۳.۶۴-fold increase in ۱۷α -OHP level, which was significantly higher than CPH (P< ۰.۰۵). Also, there was a significant increase of steroid secretion in group stimulated with ۱۰۰ µl ml-۱ of CPS and CPH, but there were no significant differences between them (P> ۰.۰۵).

Keywords:

Cyprinus carpio , Cell culture , carp GnRH , Gonadotropin hormones , Steroid hormones