Boar sperm plasma membrane protein profile: Correlation with the zona-free hamster ova bioassay

This study was designed to compare differences among porcine sperm plasma membrane proteins with the ability of spermatozoa to interact with zona-free hamster ova. Sperm plasma membrane vesicles were recovered from 24 ejaculates from 10 fertile boars, and from cauda epididymal spermatozoa from 3 fertile and 1 very subfertile boar. Solubilized sperm plasma membrane proteins were run on 1D SDS-PAGE gels, transferred to western blots, stained, and analyzed for quantity of protein per band by scanning laser densitometry. Variation in the quantities of individual sperm plasma membrane proteins in the 20 identified bands were statistically compared with the ability of spermatozoa from the same ejaculate to penetrate zona-free hamster ova. The percentages of plasma membrane protein present in 3 bands (90, 84 and 60 kD) were positively correlated with the ability of spermatozoa from the same ejaculate to fuse with zona-free hamster ova (P = 0.002, 0.01, 0.04; R = 0.53, 0.40, 0.38, respectively). The quantities of protein in 2 other bands (69 and 35 kD) were significantly but negatively correlated with the results of the zona-free hamster ova bioassay (P = 0.02, 0.01; R = -0.42, -0.37, respectively). The sperm plasma membrane profiles were quantitatively similar between the ejaculated samples and the fertile epididymal samples. Six epididymal sperm plasma membrane proteins were present in statistically different quantities in the subfertile boar sample and the 3 fertile controls. The 90 kD band positively correlated with the hamster ova bioassay in the ejaculated samples was not detected in the subfertile epididymal sperm plasma membrane sample. These results suggest that protein(s) in one or more of the 3 positively correlated ejaculated sperm plasma membrane protein bands may be involved in sperm-oocyte interaction.