Response of Pituitary Cells and Tissues to Neurokinin B and F in the Nile tilapia.

Neurokinin B (NKB) is a neuropeptide involved in the regulation of reproductive endocrine system of vertebrate animals, including fish. However, the pathway of NKB action in fish has not been clearly elucidated. In order to clarify the effect of NKB and NKF (neurokinin F) on gonadotropic hormone (GTH) gene expression in the pituitary, we studied the changes of LHβ and FSHβ gene expressions by using two different pituitary culture methods (whole pituitary culture or dispersed pituitary cell culture). Pituitaries were removed from mature female and male Nile tilapia. Changes of LHβ and FSHβ gene expressions were measured and compared after the treatment with NKB or NKF peptides at concentrations 0 to 1,000 nM. Expression of GTH genes in the whole pituitary cultures treated with NKB or NKF peptides did not show significant difference except in female at one concentration when treated with NKF. On the contrary, there were significant changes of GTH gene expressions in the dispersed pituitary cell cultures when treated with NKB and NKF peptides. These results suggest that dispersed pituitary cell culture is more relevant than whole pituitary culture in studying the function of pituitary, and that NKB and NKF could act directly on the pituitary to regulate the expression of GTH genes.