In previous studies a series of Mabs against boar capacitated sperm have been produced. One of these Mabs--4B12--was found to recognize a surface membrane-associated protein located in the acrosome portion of the spermatozoa that became accessible to antibody after capacitation. In biological experiments it was shown that Mab 4B12 significantly inhibited boar sperm-porcine ZP binding. In attempts to investigate the mechanisms by which Mab 4B12 affected sperm-ZP binding, the role of the cognate protein on some functional parameters such as sperm motility and ability of the capacitated spermatozoa to undergo AR was studied. Experimental models of premature AR and AR physiologically induced with ZP were applied to study the effect of Mab 4B12 on boar sperm AR using PSA staining to estimate the acrosome-reacted state of spermatozoa. Sperm motility characteristics were determined by the time-exposure photokinesigraphic method. The results obtained in the present study, together with previously established inhibition of sperm-ZP binding by Mab 4B12, documented the participation of the 4B12 protein in primary sperm-ZP binding. The protein is not connected with sperm motility and secondary sperm-ZP binding.

Institute of Biology and Immunology of Reproduction Bulgarian Academy of Sciences Sofia Bulgaria