ISOLATION AND CHARACTERIZATION OF MATURATION INHIBITING COMPOUND IN BOVINE FOLLICULAR-FLUID

The protein fraction which is responsible for the inhibition of matura tion of bovine oocytes in vitro was isolated from cow follicular fluid by means of column chromatography on a Sephadex G-200 and a Sepharose 4B, both in 0.1 M ammonium acetate, pH 6.7. The molecular weight of t he maturation inhibiting protein fraction is approximately 60 kDa. At a concentration of 2.0 mg/mL in cultivation medium, 100% of the oocyte s were arrested at the germinal vesicle stage. At a concentration of 0 .25 mg/mL, the protein fraction still had some meiosis inhibiting effe cts, but 56% of the oocytes were capable of maturing to the metaphase of the second meiosis (Mil). Without compact cumulus, the inhibiting f raction had no meiosis retarding effect on the oocytes. Cow follicular fluid also exhibited this inhibitory effect on oocyte maturation in v itro. However, the follicular fluid from follicles of 2.5-5.0 mm diame ter showed higher meiosis inhibiting effects than the follicular fluid from follicles of 5-10 mm diameter.