Partial Characterization of FSH Suppressing Activity (Foilicuiostatin) in Porcine Foiiicuiar Fluid Using the Metestrous Rat as an in vivo Bioassay Model

Abstract

Porcine follicular fluid can suppress serum FSH in the sham operated or acutely ovariectomized metestrous female rat (Marder et al., 1977). The active factor, called folliculostatin, was located in the retentate, but not in the filtrate, of follicular fluid filtered through an Amicon PM-10 membrane, suggesting a molecular weight of≥ 10,000. Fluid from small (1–2 mm), medium (3–5 mm) and large (6–12 mm) follicles all contained FSH suppressing activity. When compared by a two-dose factorial assay, fluid from large follicles contained a lower concentration than fluid from follicles of the two smaller sizes. The ative factor was shown to be nonsteroidal, trypsin sensitive and heat stable at 60° C for 20 min; it was inactivated after heat treatment at 80° C for 30 min. The molecular weight range and the sensitivity to proteolysis and to high temperature are characteristics similar to those of inhibin from the testis.