In vitro kallikrein treatment of human spermatozoa: stimulation of sperm penetration into zona-free hamster eggs depends on the quality of initial semen parameters but not on constituents of the kallikrein-kinin system in seminal plasma.

We investigated the effect of an in vitro kallikrein treatment of human spermatozoa on their ability to penetrate zona-free hamster eggs. Sixty-four infertility patients were classified into four groups (normo-, oligo-, astheno-, and oligoasthenozoospermia) in order to find out which men would benefit most from this procedure. An aliquot of each ejaculate was diluted with Ham's F-10 medium supplemented with human serum albumin and kept at 22C for 1 hour. Another aliquot was incubated with kallikrein (5 KU/ml.) for one hour at 22C. These sperm suspensions were then washed twice, subjected to a swim-up preparation, and subsequently incubated at 37C for 2 hours. The mean penetration rates of kallikrein-treated samples were significantly higher than those of the corresponding control assays in all but the oligoasthenozoospermia group. Our results suggest a direct proteolytic action of kallikrein because the stimulation of penetration into hamster eggs was not correlated with the amount of constituents of the kallikrein-kinin system (kinins, kininogen, kininase) in seminal plasma.