Studies Of Gonadotropin-Releasing Hormones And Its Immune Effects In Paralichthys Olivaceus

Gonadotropin-releasing hormone (GnRH) is a key message molecular of hypothalamus-pituitary-gonadal axis, plays a central role in the neuroendocrine control of the reproductive process in vertebrate, notably by stimulating synthesis and release of gonadotropins (GtH), and has been proven to be one of molecular messages to connect nerve, immunity, and endocrine system. To date, the structure and biological function of fish GnRHs and GnRH receptors have become one of hotpoints about neuroendocrinology and reproductive biology. P. olivaceus belongs to Bothidae, Pleuronectiformes, Osteichthyes, and is one of important marine aqucultural fishes in China. Information on molecular endocrinology of reproduction especially GnRH and GnRH-R is very limited in P. olivaceus. To understand types, distribution and role of GnRHs and GnRH-R is of vital significance to elucidate the interaction of nerve-rprodution-endocrine system in P. olivaceus. The results in this study are as follows:(1) Tissue distribution of GnRH and NPY was detected by immunohistochemistry method in P. olivaeus. The results showed that: GnRH positive reaction was found in nerve, peptic, and reproduction system such as brain, pituitary, stomach, intestine, ovary, and so on; NPY positive reaction was detected in spinal bulb, cerebrum and ovary.(2) A 607 bp cDNA of full-length cGnRH-II was obtained from the brain in P. olivaeus, and it encoded 95 amino acid (aa) residues of propeptide. This propeptide included a signal peptide of 23 aa residues, a matural cGnRH-II decapeptide (QHWSHGWYPG), an amidation/prosite processing signal (A/P signal, Gly-Lys-Arg) and a GnRH-associated peptide (GAP) of 49 aa residues. Homology analysis suggested that cGnRH-II propeptide of P. olivaeus is most identical to that of barfin flounder (Pleuronectdae) (97.6% identity); and in the next places are cGnRH-II propeptides of Rachycentridae, Cichlidae and Sparidae bony fish; it has lower identity to mammalian, reptile and amphibian. RT-PCR analysis suggested that cGnRH-II mRNA could be expressed in kidney, brain, pituitary, gill and ovary, among which it was expressed at...