The most potent inhibitor for sperm-oviduct binding was fucoidan, and indeed, polysaccharides like mannan and fucoidan were also highly effective in preventing fucose-PAA-biotin binding to immobilized SPM. In fact, mannan-BSA-biotin and fucoidan-biotin had higher affinity for immobilized SPM than fucose-PAA-bi-otin. We should consider here that the conjugates used differ in stoichiometry of carbohydrate and biotin moieties. The high inhibitory effect of mannan and its high binding affinity for the isolated SPM indicates that bovine sperm cells have high affinity for mannan containing glycocon-jugates.
Mannan binding may either take place during sperm-oviduct binding in bovine species or later, for example, during ZP binding, as has been suggested by Revah et al.. It would be of interest to evaluate the role of mannan in bovine sperm binding to oviduct explants as well as to the zona pellucida.
Heparin, another polysulfated glycoconjugate, is widely used to capacitate bull sperm and induces capacitation-spe-cific CTC staining in 60-70% of the sperm cells.