Angiotensin I converting enzyme in rat testis, epididymis and vas deferens under different conditions.

Angiotensin I converting enzyme (ACE) was found in the testis, epididymis and vas deferens of rats. In tissue specimens without a prior washout of seminal fluid the highest specific ACE activity was measured in the testis. The enzyme activity was significantly lower towards the end of the excurrent ducts, suggesting that the enzyme is synthesized in the testis and secreted into the seminal fluid there. An ACE inhibiting substance may be secreted by the epididymal epithelium. Enzyme synthesis and enzyme inhibition are probably under simultaneous endocrine control. In-vitro inhibition, pH- and temperature-dependence of gonadal ACE correspond with that of lung and blood plasma. However, the physiological function of the enzyme on sperm motility and fertility remains unsolved.