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 enhances 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 divided into two equal aliquots. An equal volume of heat-inactivated cow's milk (95 degrees C, 10 minutes) was added to one aliquot and an equal volume of TEST-yolk was added to the other aliquot. Both sperm mixtures were cooled slowly to 5 degrees C and incubated for 2 hours. They were then washed twice (400 x g for 8 minutes) with culture medium at 37 degrees C and processed for SPA and HZA.

MAIN OUTCOME MEASURES

Percentage 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 penetration index and the number of sperm bound were high but were not statistically significant.

CONCLUSION

Preincubation of sperm in milk enhances the SPA and HZA outcome when compared with TEST-yolk.