Evaluation of the effect of butyl p-hydroxybenzoate on the proteolytic activity and membrane function of human spermatozoa.

The inhibition of the proteolytic activity of acrosin in human spermatozoa by butyl p-hydroxybenzoate was assessed by the gelatin substrate film method. Compared with a typical acrosin inhibitor, TLCK, the inhibitory activity of butyl p-hydroxybenzoate to acrosin was much more effective (20 times) than that of TLCK, proving that butyl p-hydroxybenzoate was a potent acrosin inhibitor. The effect of butyl p-hydroxybenzoate on membrane function of human spermatozoa was evaluated using a sperm-tail hypoosmotic swelling test and supravital stain method. A good correlation (r = 0.92) was observed between the % spermatozoa with normal membrane function and the % live spermatozoa after treatment of the spermatozoa with butyl p-hydroxybenzoate for 1 min, indicating that the death of spermatozoa caused by butyl p-hydroxybenzoate is probably due to impairment of sperm membrane function. Both the inhibitory effect on acrosin and the adverse effect on membrane function suggest that butyl p-hydroxybenzoate could be developed as a new vaginal contraceptive.