Abstract: Abstract: The present study aimed to identify the distribution of D-galactosyl residue on zona pellucida (ZP) and its function(s) in sperm binding and penetration in vitro in pig. In vitro matured pig oocytes were freed from cumulus cells and treated for 30 mins with fluorescein isothiocyanate(FITC)-labeled lectin Bandeiraea simplicifolia lectin-I (BS-I) and Ricinus communis agglutinin (RCA-I) to examine alpha-D-galactosyl residue and beta-D-galactosyl residue respectively. When examined under a fluorescence microscope, both BS-I and RCA-I were bound to the ZP and most of them accumulated in the outer surface of the ZP. Among them, bound BS-I showed weaker fluorescence but bound RCA-I showed stronger fluorescence especially in the outer surface of the ZP. The treated oocytes were inseminated in vitro and after 2 or 12h insemination, the sperm-oocyte binding and penetration were examined. The results showed that after treatment of RCA-I, the sperm binding number was inhibited (18 vs 95) and sperm penetration was completely blocked; after treatment of BS-I, the sperm binding number was slightly inhibited (59 vs 95) and sperm penetration was not influenced. These results suggested that beta-D-galactosyl residue in the pig ZP glycoprotein may act as an important sperm receptor for sperm-oocyte binding and penetration.

Key words: sperm receptor, pig zona pellucida, glycoprotein, beta-D-galactosyl residues, Lectin