The effect of some proteinase inhibitors on liquefaction of human semen.

This study examined the effect of some proteinase inhibitors on liquefaction of human semen. It revealed that a strong plasmin inhibitor, 6-amidino-2-naphthyl-6-guanidinobenzoate dihydrochloride (Fusan) showed a significant inhibition of liquefaction, while t-amino caproic acid (t-ACA) showed a weak retardation effect. In terms of sperm quality after liquefaction, Fusan (10 mM), ethyl diamine tetra-acetic acid (EDTA) and Urinastatin completely inhibited sperm motility. Fusan (1 mM) and Lima bean trypsin inhibitor (LBTI) decreased sperm motility significantly, while leupeptin and t-ACA had little effect. Leupeptin, LBTI, t-ACA and Fusan (1 mM) did not affect sperm speed. 50% inhibition of sperm motility was calculated to be approximately 1.7 mM of Fusan concentration. In addition, two inhibitors, Chymostatin and Phosphoramidon were also tested with each experiment and had no effect on liquefaction or on sperm motility and speed. These results strongly suggest that plasmin may play an important role in the liquefaction process of human semen.