[The effect of kallikrein and caffeine on the sperm survival of cryopreserved semen in patients with oligozoospermia].

Cryopreservation of semen from patients with oligozoospermia (sperm counts less than 20 million/ml) generally results in a severe decline in the percentage of motile spermatozoa after thawing in comparison with normozoospermia. We studied the effects of two metabolically active compounds, namely kallikrein and caffeine, on the survival of frozen-stored spermatozoa, in particular, from patients with oligozoospermia. A modified Ackerman's solution was used as the protective medium, and the specimens were frozen using a programmed freezer. We evaluated the post-thaw survival rate of spermatozoa by sperm counts on addition of agents. 1) When used the modified Ackerman's solution only, the post-thaw survival rate in the cases of oligozoospermia was significantly lower than that in the cases of normozoospermia. On the other hand, between these groups, there were no significant differences in the post-thaw activity rates of spermatozoa. 2) When added 1 KE/ml kallikrein and 7.5 mM caffeine (final volume) to the protective medium, the survival rate in the cases of oligozoospermia increased significantly, so that no significant differences were seen in the survival rates between the groups of oligozoospermia and normozoospermia. The effect of caffeine was better than that of kallikrein. 3) It was suggested that kallikrein and caffeine activated the non-motile live spermatozoa after thawing especially in the cases of oligozoospermia.