Inhibition of Oocyte Maturation by Porcine Follicular Fluid: Partial Characterization of the Inhibitor1

Abstract

The present study was undertaken in order to characterize further the inhibitory activity of porcine follicular fluid (FFl) upon the spontaneous maturation of isolated oocytes. The inhibitory action of FFl upon oocyte maturation was not destroyed by heating to 60°C or by repeated freezing and thawing and could not be removed by extraction with charcoal. The inhibitory action was, however, abolished by trypsin digestion. The activity was concentrated by Amicon UM-2 membrane filtration. Further purification was achieved by the use of Sephadex G-25 column chromatography. The data are consistent with the suggestion that the inhibitor is a peptide with a molecular weight of about 2,000. The inhibitory activity of FFl could be overcome by the addition of ovine LH (5 μg/ml) to the culture medium but not by bovine prolactin (10 μg/ml) or dibutyryl cyclic AMP (0.04–0.4 mM).