Effects of Kiss2 on the Expression of Gonadotropin Genes in the Pituitary of Nile Tilapia ().

Kisspeptin, expressed mainly in the hypothalamus, stimulates gonadotropin-releasing hormone neurons to facilitate reproduction. In some model animals, the kisspeptin is also expressed in the pituitary. Recently, a pathway has been suggested in which kisspeptin acts directly on the pituitary to secretion of gonadotropin in mammals. In the present study, pituitaries of the Nile tilapia () were cultured at different concentrations of kisspeptin-10 (Kp-10, FNYNPLSLRF) for 3 hours to observe the effect of kisspeptin on the expression of follicle-stimulating hormone β subunit () gene and luteinizing hormone β subunit () gene. Pituitary tissues were cultured with 0.1 μM of Kp-10, luteinizing hormone releasing hormone (LHRH), or LHRH+Kp-10 for 3, 6, 12, and 24 hours to investigate changes in the expression of and mRNA. Pituitaries cultured with high concentration of Kp-10 more than 0.1 μM for 3 hours exhibited a significant increase of mRNA expression, but not mRNA. The expression of both and mRNA increased after 6 hours in 0.1 μM of Kp-10 medium in comparison with that in the control medium. Tissues cultured in the LHRH medium however exhibited increased expression of both genes not only at 6 but also 12 hours. There were no significant differences of and gene expression in tissues cultured with LHRH+KP-10 medium compared with the control. These results suggested that although kisspeptin plays an important role in and expression in the pituitary of Nile tilapia, its action is far more complicated than expected.