Interaction of boar spermatozoa with porcine oocytes: Increase in proteins with high affinity for the zona pellucida during epididymal transit

Cauda boar sperm but not caput sperm bind to isolated porcine oocytes, and several cauda sperm plasma membrane proteins (PMPs) with high affinity for isolated zonae have been identified. These PMPs migrate with apparent molecular weights near 70, 45 and 30 K [Peterson et al, Gamete Res 12: 91–100, 1985]. When caput plasma membranes (PM) were fractionated on dextran sulfate (DS) agarose and compared to cauda PM similarly fractionated, less protein with high affinity for DS bound to the column, and significant differences in the PMPs eluted with increasing concentration of NaCl were observed. The PMPs at ∼70, ∼45, and ∼30 K, noted above, and two bands near ∼20K were present in fractions from cauda PM but were absent or present in only small quantities in caput PM. Cauda PM fraction eluted at high salt were effective in blocking the binding of sperm to isolated oocytes; caput PM fractions were not. Antibodies to the cauda PMPs eluted at high salt, which blocks the binding of capacitated sperm to eggs and fertilization in vitro, were absorbed by cauda PMV but not by caput PMV. These findings suggest that the ability of boar sperm to attach to porcine oocytes develops as the result of the addition of one or more of these PMPs to sperm during epididymal transit.