Abstract

Objective: To determine the contribution of the polysulfate-binding domain (PSBD) of acrosin during sperm penetration. Design: To inhibit the in vitro fertilization of mouse zona-intact oocytes by using a polyclonal antibody raised against an 18-amino acid peptide of proacrosin (anti-PSBD). Setting: Unit of Reproduction and Development, Faculty of Biological Sciences, Pontifical Catholic University of Chile. Patient(s): None. Intervention(s): A polyclonal antibody against the 43IFMYHNNRRYHTCGGILL60 peptide was raised in New Zealand female rabbits. The specificity of the antibody was evaluated by an ELISA. Zona-intact mouse oocytes were coincubated with capacitated spermatozoa for 3 hours in the presence of 0.63 mg/mL of the antibody or preimmune serum. As a control, we used zona-free mouse oocytes under the same experimental conditions. Main Outcome Measure(s): We evaluated the fertilization rate of zona-intact and zona-free mouse oocytes by phase-contrast microscopy. An oocyte was considered fertilized when at least one decondensed sperm head was found within the egg cytoplasm. We evaluated 50-60 mouse oocytes in each group in three independent experiments. Result(s): The anti-PSBD antibody inhibited the fertilization of zona-intact, but not zona-free, mouse oocytes, by capacitated spermatozoa. In addition, the binding of the anti-PSBD to proacrosin/acrosin in a solid-phase assay was inhibited in the presence of polysulfates (fucoidan). Conclusion(s): The anti-PSBD directed against the PSBD of proacrosin/acrosin inhibited the penetration of capacitated mouse spermatozoa through the zona pellucida. This antibody may be a useful tool to define the roles of the different domains of proacrosin/acrosin during gamete interaction. © 2002 by American Society for Reproductive Medicine.