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 15.7Â±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.
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