ISOLATION AND CHARACTERIZATION OF GONADOTROPIN ISOHORMONES FROM THE PITUITARY GLAND OF PIKE EEL (MURAENESOX CINEREUS)

Pike eel gonadotropins were isolated from pituitary glands by 40% alcohol‐6% ammonium acetate, pH 5.1 extraction and were purified by DEAE‐cellulose chromatography and electrophoresis into four electrophoretically homogeneous forms. These four isohormones were biologically identified as gonadotropins by the stimulation of ³²P‐uptake in 1‐day‐old chick testes, by the induction of ovulation in catfish, and by the in vitro production of testosterone from isolated rat Leydig cells and of androgen from carp testes. The amino acid composition of the isohormones were similar to other known piscine gonadotropins (carp and salmon) and were composed of two non‐identical subunits with Tyr and Ser as N‐terminal amino acid residues. The molecular weights of two subunits were 15 000 and 10 500, respectively, as estimated by SDS‐gel disc electrophoresis.