Identification of the second gonadotropin-releasing hormone in chicken hypothalamus: evidence that gonadotropin secretion is probably controlled by two distinct gonadotropin-releasing hormones in avian species.
A new peptide having gonadotropin-releasing activity distinct from the known luteinizing hormone-releasing hormones ( LHRHs ) has been identified in a chicken hypothalamic extract. The existence of [Gln8]LHRH in avian hypothalamus has been reported previously. The new molecular species of gonadotropin-releasing activity, named chicken gonadotropin-releasing hormone II (chicken GnRH-II), has been isolated recently in a yield of 7 micrograms, starting from 10,000 chicken hypothalami. Structural analyses have been performed on the peptide fragments derived from chymotryptic and thermolytic digests of chicken GnRH-II by amino acid analyses and terminal analyses. The full sequence of chicken GnRH-II has been determined to be: pGlu-His-Trp-Ser-His-Gly-Trp-Tyr-Pro-Gly-NH2. A synthetic decapeptide with the above sequence was verified to be chromatographically identical to natural chicken GnRH-II. For further structural confirmation, chymotryptic and thermolytic peptides from synthetic and natural chicken GnRH-II also were identified. Thus, the structure of chicken GnRH-II has been definitely established. The gonadotropin-releasing potency of chicken GnRH-II was about 32% of that of mammalian LHRH and 8 times more potent than chicken LHRH, as estimated from the bioassay with rat anterior pituitary cells. Our results indicate that gonadotropin secretion is probably controlled by two distinct GnRHs , at least in avian species.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002645:Chickens / Q000502:physiology*; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology; D007030:Hypothalamo-Hypophyseal System; D007031:Hypothalamus / Q000032:analysis*; D007986:Luteinizing Hormone / Q000378:metabolism; D010906:Pituitary Hormone-Releasing Hormones / Q000032:analysis*
D000596:Amino Acids; D010906:Pituitary Hormone-Releasing Hormones; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone