Further studies of inhibitors of in vitro mammalian oocyte maturation.

Studies of luteinizing hormone (LH)-mediated serum inhibition and of follicular fluid and granulosa cell inhibition of in vitro porcine, ewe, and cow oocyte meiotic maturation have been carried out. A porcine serum inhibitor or inhibitors with a molecular weight above 15,000, similar to the ewe and cow serum inhibitor(s), have been demonstrated. An LH-inactivated inhibitor or inhibitors in fluid from medium-sized ewe and cow follicles have been shown and a minimally effective porcine follicular fluid inhibitor has been confirmed. The estimated molecular weight of these inhibitors is below 1,000. Granulosa cells from the three species were not found to be dramatically inhibitory. It is postulated that the follicular fluid inhibitor(s) may be derived from the larger serum molecule(s) by an action of LH within an intermediate cell type.