Assay of testicular angiotensin-converting enzyme activity in human spermatozoa

The testicular isozyme of angiotensin-converting enzyme (ACE) is associated with male fertility. Spermatozoa from mice lacking ACE showed defects in t ransport within the oviducts and in binding to zonae pellucidae although th e animals had normal sperm count, morphology and motility. In fact, unexpla ined infertility is difficult to be predicted by conventional parameters su ch as sperm count. We measured membrane testicular ACE activity in a sperm suspension in PBS and total testis ACE activity in spermatozoa by solubiliz ation with Triton X-100. Total testis ACE activity and membrane testis ACE activity of the same subject were compared in 12 control subjects. We demon strated that testicular ACE is stable in spermatozoa and the assay of testi cular ACE activity is possible. Total testicular ACE activity was approxima tely twice the membrane testicular ACE activity in all of the subjects test ed. The assay of testicular ACE activity in human spermatozoa could be a ne w method for the assessment of sperm function.