Characterization of brain gonadotropin-releasing hormone (GnRH) molecular variants in brain extracts from different perciform fishes from Antarctic waters

Gonadotropin-releasing hormone (GnRH) is the hypothalamic hormone that regu lates the reproductive system by stimulating release of gonadotropins from the anterior pituitary gland. The molecular variants of the reproductive ne uropeptide GnRH were characterized from brain tissue of three perciform spe cies from Antarctic waters: Pseudochaenichthys georgianus, Chaenocephalus a ceratus, and Notothenia rossi. The study involved reverse phase high-perfor mance liquid chromatography (RP-HPLC) followed by radioimmunoassay (RIA) wi th two antisera that recognize all GnRH variants already identified: PBL 45 and PBL 49. The results showed that brain extracts of P. georgianus, C. ac eratus, and N. rossi contain, like those of other perciform fish, three for ms of GnRH likely to be: sbGnRH (seabream GnRH), cGnRH-II (chicken GnRH II) and sGnRH (salmon GnRH). They also showed evidence for the presence of a f ourth GnRH variant, chromatographically and immunologically different from the other known forms of the vertebrate hormone. Although final conclusions will require isolation, purification, and sequencing of these molecules, t hese results offer encouraging possibilities of further advances in the cha racterization of a multiplicity of GnRH molecular variants.