Presence of Salmon Gonadotropin-Releasing Hormone (GnRH) and Compounds with GnRH-Like Activity in the Ovary of Goldfish1

The presence of ovarian GnRH and/or compounds with GnRH-like activity was investigated in the goldfish ovary. Goldfish ovary was extracted using an acetone/HCl/ether mixture and was purified by Waters C-18 Sep-Pak columns (ovarian extract). The goldfish ovarian extract was found to 1) stimulate gonadotropin release and subunit messenger RNA production in the goldfish pituitary that was inhibited by a GnRH antagonist; 2) stimulate germinal vesicle breakdown in the prophase-I arrested follicle-enclosed goldfish oocytes in vitro, which was inhibited by a GnRH antagonist; 3) immunoreact with various GnRH antisera; and 4) bind to GnRH receptors in the goldfish pituitary and ovary as well as rat pituitary. Further purification with HPLC revealed the presence of two compounds with GnRH-like activity. One with identical chromatographic characteristics, amino acid composition, and primary structure to that of the salmon GnRH (sGnRH), and the other a novel compound with GnRH-like activity.