Comparative analysis of motility characteristics of Percoll-selected spermatozoa populations from fresh and cryopreserved semen.

The proportion and quality of motility of spermatozoa in normozoospermic ejaculates were assessed using computer-assisted semen analysis. The ejaculate was split and the motility re-assessed following separation on a Percoll gradient with or without cryomedium and cryopreservation. Cryopreservation caused a significant decrease in the proportion of motile spermatozoa and in their velocity and amplitude of lateral head displacement. The initial decrease in the proportion of motile spermatozoa was found to be in part an effect of the cryomedium. The use of Percoll gradient separation did not initially change these effects but after 4 h incubation differences in velocity and amplitude of lateral head displacement between samples were no longer evident. Percoll-selected, cryopreserved spermatozoa had both a stable proportion of motile spermatozoa and a stable velocity for at least 48 h, whereas in fresh spermatozoa populations, similarly separated using Percoll, the proportion of motile spermatozoa had decreased by 24 h and the velocity was lower at 48 h. Percoll preparation is an effective method for the selection of motile spermatozoa from cryopreserved semen which, after a short incubation, have similar motility characteristics to fresh spermatozoa.