To evaluate sperm membrane system integrity in unexplained infertile male subjects with three consecutive conception failures on IUI even though semen clinical parameters were normal. Prospective study. Medical biotechnology laboratory, School of Medical Science and Technology IIT Kharagpur, India. Twenty-nine patients with unexplained infertility, 17 normal proven-fertile healthy donors, and 21 infertile males with low motility but with other semen parameters remaining normal. Semen samples were collected from unexplained infertile patients as well as from healthy fertile donors after abstinence of 3-5 days and were analyzed according to World Health Organization guidelines. Release of 5'-nucleotidase (plasma membrane marker), lactate dehydrogenase (mitochondrial marker) and free acrosin, proacrosin, and total acrosin (acrosomal membrane marker). Plasma membrane integrity and respiratory activity of sperm cells were comparable in all three groups. The proacrosin-acrosin system was adversely affected in unexplained infertile subjects despite high sperm motility. Total acrosin activity may be considered as a sensitive biochemical marker for clinical evaluation of unexplained infertility in males.
