Lack of association between polymorphisms in the testis-specific angiotensin converting enzyme gene and male infertility in an Asian population.

Angiotensin converting enzyme (ACE) is a membrane-bound dipeptidyl carboxy-peptidase that generates vasoconstricting angiotensin II and inactivates vasodilating bradykinin. The ACE gene encodes two isozymes: the somatic isozyme (sACE) is found in many tissues including vascular endothelial cells, whereas the testis-specific isozyme (tACE) is expressed exclusively in developing spermatids and mature sperm. Thus, ACE might have physiological functions in addition to blood pressure regulation. Male mice lacking tACE activity show reduced fertility, indicating its importance in male fertility. In this study, we screened five recently defined tACE gene polymorphisms in 90 Singapore Chinese men with infertility and 84 fertile controls using PCR-based restriction fragment length polymorphism and DNA sequencing. However, only one of these polymorphisms was identified in both patient and control groups, the frequency of which was not significantly different in patients and controls. Thus, these ACE gene polymorphisms are unlikely to contribute to the pathogenesis of male infertility in the Singapore Chinese population.