Seasonal expression and distribution of kisspeptin1 (kiss1) in the ovary and testis of freshwater catfish, Clarias batrachus: A putative role in steroidogenesis

The central role of kisspeptin (kiss) in mammalian reproduction is well established; however, its intra-gonadal role is poorly addressed. Moreover, studies investigating intra-gonadal role of kiss in fish reproduction are scanty, contradictory and inconclusive. The expression of kiss1 mRNA has been detected in the fish brain, and functionally attributed to the regulation of reproduction, feeding and behavior. The kiss1 mRNA has also been demonstrated in tissues other than the brain in some studies, but its cellular distribution and role at the tissue level have not been adequately addressed in fish. Therefore, an attempt was made in the present study to localize kiss1 in gonadal cells of the freshwater catfish, Clarias batrachus. This study reports the presence of kiss1 in the theca cells and granulosa cells of the ovarian oocytes and interstitial cells in the testis of the catfish. The role of kiss1 in the ovary and testis of the catfish was also investigated using kiss1 receptor (kiss1r) antagonist (p234). The p234 treatment decreased the production of 17 beta-estradiol in ovary and testosterone in the testis by lowering the activities of 3 beta-hydroxysteroid dehydrogenase and 17 beta-hydroxysteroid dehydrogenase under both, in vivo as well as in vitro conditions. The p234 treatment also arrested the progression of oogenesis, as evident from the low number of advancing/advanced oocytes in the treated ovary in comparison to the control ovary. It also reduced the area and perimeter of the seminiferous tubules in the treated catfish testis. Thus, our findings suggest that kiss is involved in the regulation of gonadal steroidogenesis, independent of known endocrine/autocrine/paracine regulators, and thereby it accelerates gametogenic processes in the freshwater catfish.

Automated summary

This study investigated the presence of kisspeptin in the gonadal cells of the freshwater catfish and its role in the regulation of steroidogenesis. The results showed that kisspeptin plays a role in accelerating gametogenic processes by affecting the production of 17 beta-estradiol and testosterone in the ovary and testis of the catfish, respectively. Additionally, the study found that kisspeptin receptor antagonist treatment led to a decrease in activities of key enzymes involved in steroid hormone production and arrested the progression of oogenesis and spermatogenesis in the treated catfish.