Sperm acrosin: liberation from the acrosome and activity of the free proteinase in the presence of nonoxinol-9.

The effects of the non-ionic detergent nonoxinol-9 and a vaginal contraceptive containing nonoxinol-9 on the liberation of the cellular proteinase acrosin from human spermatozoa and on the activity of the solubilized proteinase were investigated. Detachment of acrosin from the acrosome was observed in the presence of 0.01 to 1% nonoxinol-9 as assessed by activity assays and the gelatin substrate film technique. Activity of the free proteinase was modulated by nonoxinol-9 in a biphasic manner, i.e. lower concentrations of the detergent (0.001 to 0.1%) stimulated the activity of acrosin up to 180%, while higher concentrations of the detergent (1%) resulted in an extensive inhibition of acrosin (30% residual activity). It is demonstrated that local intravaginal nonoxinol-9 concentrations of 1% equalling the post-coital concentration of the intravaginal suppository Patentex oval when properly applied will result in an effective inhibition of the liberated sperm proteinase acrosin thus preventing unspecific proteolysis of the vaginal epithelia.