Involvement of sperm sulphatases in early sperm-zona interactions in the hamster

Sulphatase preparations from Abalone entrails, the limpet Patella vulgata and ox liver, as well as artificial substrates for these enzymes, were used in the hamster in vitro fertilization system to study the possible roles of sperm sulphatases in sperm-zona pellucida interactions. p-nitrophenyl sulphate, p-nitrocatechol sulphate, ascorbate 2-sulphate, as well as D-glucopyranose and D-galactopyranose, both sulphated at the 3, 4 or 6 position but not the 2 position, inhibited fertilization in a dose-dependent manner. Sperm-egg fusion was not inhibited by the substrates used and eggs pre-treated with sulphates could readily be fertilized. Sperm motility and therefore viability was unaffected by inhibitory concentrations of substrates as determined by rhodamine 123 labelling of motile spermatozoa. Acrosomal integrity of rhodamine-labelled spermatozoa was assessed and found to be unaffected by inhibitory levels of substrates. Fertilization was inhibited by high concentrations of the two molluscan sulphatases but not by purified ox liver sulphatase. Pre-treatment of eggs with these enzymes did not prevent fertilization. Long-term exposure of hamster oocytes to N-acetylhexosaminidase or limpet sulphatase caused thinning and distension of the zona pellucida but these changes were not observed with the ox liver sulphatase. The results suggest that a glycosulphatase is probably released from hamster spermatozoa during sperm-egg adhesion and, or, penetration. If sperm-egg adhesion molecules are sulphated, the commercially available sulphatases would be unsuitable for their characterization.