THE EFFECT OF PREINCUBATION OF HUMAN SPERMATOZOA IN MILK ON SPERM PENETRATION INTO ZONA-FREE HAMSTER OOCYTES AND ON SPERM BINDING TO THE HUMAN ZONA-PELLUCIDA

Objective: To determine whether preincubation of sperm in milk enhance s the outcome of sperm penetration assay (SPA) and hemizona assay (HZA ) when compared with preincubation in TES and Tris (TEST)-yolk. Design : Sperm penetration assay and HZA were performed on milk and TEST-yolk preincubated spermatozoa. Interventions: Ejaculates were washed and d ivided into two equal aliquots. An equal volume of heat-inactivated co w's milk (95 degrees C, 10 minutes) was added to one aliquot and an eq ual volume of TEST-yolk was added to the other aliquot. Both sperm mix tures were cooled slowly to 5 degrees C and incubated for 2 hours. The y were then washed twice (400 X g for 8 minutes) with culture medium a t 37 degrees C and processed for SPA and HZA. Main Outcome Measures: P ercentage of oocytes penetrated and the penetration index for the SPA. The number of sperm bound to hemizona and hemizona index for the HZA. Results: Sperm preincubated in milk yielded significantly higher SPA results and hemizona index when compared with TEST-yolk. The penetrati on index and the number of sperm bound were high but were not statisti cally significant. Conclusion: Preincubation of sperm in milk enhances the SPA and HZA outcome when compared with TEST-yolk.