Fish gonadotropin(s). III. Evidence for more than one gonadotropin in chum salmon pituitary glands.

Two proteins with gonadotropin activity have been isolated from a highly purified chum salmon (Oncorhynchus keta) gonadotropin preparation (G-75 Fraction II) by chromatography on DEAE Bio Gel A. These gonadotropins exhibited distinct behaviour in polyacrylamide gel electrophoresis, chromatography on Sephadex G-75 superfine, and ratios of cAMP stimulation in immature rainbow trout ovaries and testes. Rechromatography of G-75 Fraction II on Sephadex G-75 superfine gave a symmetrical protein peak with a coincident cAMP activity profile. Repeated freezing and thawing elicited a shift in the cAMP activity profile toward the trailing edge of the protein peak. Data are discussed in terms of two gonadotropin molecules which respond differently to phase changes. Charge polymorphism was exhibited by isoelectric focusing in polyacrylamide gels of one of the DEAE fractions. Five UV absorbing bands were observed which stimulated cAMP production in immature rainbow trout gonads. Three of these bands increased adenyl cyclase activity in trout ovaries and testes. One of the bands stimulated cAMP production primarily in trout testes and the other stimulated trout ovaries, providing evidence for two gonadotropins, each of which is sex specific.