EFFECT OF BOVINE OVIDUCTAL ESTRUS-ASSOCIATED PROTEIN ON THE ABILITY OF SPERM TO CAPACITATE AND FERTILIZE OOCYTES

At estrus, an oviduct-specific, estrus-associated glycoprotein (EAP) o f molecular weight 85-95,000, is secreted by the oviductal epithelium and found in cannula-derived bovine oviductal fluid (ODF). The objecti ves of these studies were to determine if bovine sperm were capacitate d by EAP in vitro, whether this effect differed for EAP derived from O DF versus conditioned medium from oviduct ampullar explants, and to de termine if sperm capacitated in vitro with EAP-fertilized bovine eggs. Sperm were incubated for up to 6 hours with partially purified EAP de rived from ODF and assessed for capacitation by their ability to under go the acrosome reaction following exposure to lysophosphatidylcholine . At 4 hours of incubation, the number of capacitated sperm in treatme nts containing 50% ODF or EAP plus bovine serum albumin (BSA) was simi lar, and it was significantly greater than the number of capacitated s perm in treatments containing antibodies to EAP. Using purified EAP de rived from ampullar explant-conditioned medium, twice the number of sp erm were capacitated after 4 hours with EAP from conditioned medium or with ODF than with treatments containing anti-EAP. The fertilizing ab ility of sperm incubated with EAP was significantly greater than that for sperm incubated without EAP or with anti-EAP. We conclude that bov ine EAP, derived from both ODF and in vitro cultures, promotes sperm f ertilizing ability.