MODULATION OF GONADAL STEROIDS PRODUCTION BY TILAPIA PITUITARY EXTRACT: AN EVALUATION THROUGH IN-VITRO AND IN-VIVO STUDIES

Objective : Endocrine regulation strategies are widely used for synchronization of fertility, but in some cichlids species, the treatments are not always effective. This study used tilapia ( Oreochromis niloticus ) as a model cichlid fish to evaluate homologous pituitary extract in-vitro and in-vivo bioassays. Methods : In this study, guinea pig Leydig cells, tilapia follicular cells, and female tilapia were treated with tilapia pituitary extract (TP) to evaluate the ability of TP to modulate steroid production in-vitro and in-vivo . Sex steroid hormone quantification was performed using enzyme immunoassay (ELISA), and the relative vitellogenin (Vtg) level was measured using Western blot during the maturation cycle of female fish. Results : Treatment with TP in-vitro significantly increased testosterone and estradiol (E2) levels in guinea pig Leydig cells and in tilapia follicular cells, respectively. In-vivo experiments showed a significant increase in plasma E2 and Vtg concentration in the TP-treated female. Interestingly, 40% oocyte maturation was observed in TP-treated adult female tilapia whereas, only 7% was observed in the control group. TP treatment is increased relative fecundity significantly, reaching a production of 15.7±5.8 oocytes/g of female. Conclusion : The outcome of this study suggests that TP has a potential use in the control of cichlid fish reproduction and can be used as an alternative method for fish fry production.