Effect of GnRH analogue on steroidogenesis in the teleost fish striped murrel (Channa striata).

The striped murrel (Channa striata) is a high-value food fish in Southeast Asia; however, captive breeding success has remained limited due to a lack of knowledge about its reproductive physiology. This study examined the impact of synthetic gonadotropin-releasing hormone analogue (sGnRHa) on the reproductive biology of females. Brooders (450-650 g) were administered sGnRHa at 0.4 mL/Kg for male and 0.6 mL/Kg for female brooders (n = 18) and 0.9% saline as a control (n = 6). To assess temporal steroidogenic responses, samples were collected at 0, 6, and 12 h post-injection. qPCR analysis was used to examine the expression of key steroidogenic genes, while enzyme immunoassay measured serum concentrations of estradiol, vitellogenin, and progesterone. Results indicate significant temporal responses to sGnRHa treatment. The StAR gene exhibited the most pronounced response at 6 h of post-injection. Cyp17α and Hsd17β showed peak expression at 6 h, coinciding with maximum serum estradiol (380 ± 18 pg/mL) and vitellogenin (28 ± 3 ng/mL) concentrations. Cyp19a and Hsd3β demonstrated delayed responses, reaching peak expression at 12 h. Progesterone levels were elevated at 6 h of post-injection, from a baseline of 240 ± 15 pg/mL to 310 ± 18 pg/mL. Histological examination revealed partial induction and did not show a significant change after treatment. The coordinated temporal regulation indicates that sGnRHa effectively stimulates the steroidogenesis. Early up-regulation of StAR, Cyp17α, and Hsd17β drives estrogenic activity and vitellogenesis, while delayed activation of Cyp19a and Hsd3β facilitates maturation. These findings provide insights into reproductive physiology and contribute to optimising captive breeding protocols of C. striata for sustainable aquaculture.