Isolation and characterization of a bovine seminal plasma protein inhibiting pituitary FSH secretion.

A basic protein with inhibin-like activity was purified from bull seminal plasma by ethanol precipitation, ion-exchange chromatography, gel filtration and preparative disc electrophoresis. The protein migrated rapidly into the acrylamide gel at pH 4.5 but failed to penetrate the gel at pH 8.9. Electrophoresis at pH 4.5 revealed heterogeneity. Its molecular weight by SDS gel electrophoresis was estimated to be approx. 18 000 daltons. It exhibited inhibin activity in both in vivo and in vitro model systems. The partially purified protein fraction was active in suppressing hCG-induced mouse uterine weight in immature mice. It specifically inhibited the castration-induced rise in serum FSH in 34-day-old male rats, blocked the action of synthetic LH-RH in vivo and in vitro in rats and mice respectively.