Steroidogenesis by isolated porcine oocyte‐cumulus complexes: Lack of an inhibitory effect of low molecular weight fraction of porcine follicular fluid on conversion of androgen to estrogen

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Abstract
The ability of isolated porcine oocyte‐cumulus complexes to secrete progesterone and convert androgens to estrogen during two days of culture was examined. We studied the effects of steroids, as well as a partially purified fraction of follicular fluid oocyte maturation inhibitor (Sephadex Peak A OMI), on the ability of oocyte‐cumulus complexes to mature and convert androgen to estrogen.The addition of 0.014, 0.14 or 1.4 μg/ml androstenedione to the culture medium resulted in a substrate dose‐dependent accumulation of estrogen in the culture medium after two days. Oocyte‐cumulus cell complexes secreted more estrogen in the presence of androstenedione than in the presence of testosterone (P < 0.05). The addition of 1.4 μg/ml testosterone, androstenedione, or estradiol, but not dihydrotestosterone, inhibited cumulus cell progesterone secretion (P < 0.001 versus untreated control culture). Oocyte maturation was not altered by the addition of steroids in doses up to and including 1.4 μg/ml. The Sephadex Peak A OMI fraction of pFFL inhibited oocyte maturation 51% (P < 0.01) and progesterone secretion 91% (P < 0.01) but had no effect on the conversion of androgens to estrogens. Cumulus cell monolayer formation was inhibited 71.5% (P < 0.01) by the Sephadex Peak A OMI fraction and 35.4% (P < 0.05) by the Sephadex Peak A OMI fraction plus androstenedione.These studies indicate that porcine oocyte‐cumulus complexes can convert androgens to estrogens and that partially purified OMI does not inhibit conversion of androgens to estrogen.