Primary structure and function of three gonadotropin-releasing hormones, including a novel form, from an ancient teleost, herring

The evolution of GnRH and the role of multiple forms within the brain are e xamined. Three forms of GnRH were purified from the brain of Pacific herrin g (Clupea harengus pallasi) and characterized using Edman degradation and m ass spectrometry. Two forms correspond with the known structures of chicken GnRH-II and salmon GnRH that are found in many vertebrate species. The thi rd form, designated herring GnRH (hrGnRH), has a primary structure of pGlu- His-Trp-Ser-His-Gly-Leu-Ser-Pro-Gly-NH2. This novel peptide is a potent sti mulator of gonadotropin II and GH release from dispersed fish pituitary cel ls. The content of hrGnRH in the pituitary was 8-fold that of salmon GnRH a nd 43-fold that of chicken GnRH-II, which provides supporting evidence that hrGnRH is involved in the release of gonadotropin. Herring is the most phylogenetically ancient animal in which three forms of GnRH have been isolated and sequenced. Our evidence suggests that the exis tence of three GnRHs in the brain of one species 1) is an ancestral conditi on for teleosts, 2) has the potential for separate regulation of the distin ct GnRHs, and 3) may be an evolutionary advantage for refined control of re production in different environments.