Anti-mouse sperm monoclonal antibody, A-1, inhibits sperm capacitation, acrosome reaction and calcium influx into spermatocytes.

An anti mouse sperm monoclonal antibody (A-1) inhibited sperm penetration into the egg zona pellucida and bound to an acrosomal area of sperm. In this study, we examined whether or not the antibody affects the sperm capacitation and the acrosome reaction. Sperm were incubated in modified Krebs-Ringer bicarbonate medium in the presence or absence of the antibody. The capacitation of sperm was assessed by chlortetracycline fluorescence pattern assay. The percentage of capacitated sperm did not increase in the presence of antibody, but increased time-dependently in its absence. The acrosome reaction of the capacitated sperm was induced by the addition of ionophore. The ionophore, however, failed to induce the reaction in the presence of the A-1 antibody. Next, the calcium influx into spermatocytes was examined. The capacitated sperm, preloaded with Fura-2, were treated with ionomycin in the presence or absence of the A-1 antibody. The influx of calcium ions into capacitated spermatozoa was also inhibited by the antibody. Thus a monoclonal antibody, A-1, inhibited the sperm capacitation, acrosome reaction and calcium influx into spermatocytes.