A genetic study of angiotensin I-converting enzyme levels in human semen.

The plasma level of angiotensin I-converting enzyme (ACE) has been shown to be under genetic control. An insertion/deletion polymorphism in the ACE gene is associated with differences in the level of ACE in the plasma and inside T-lymphocytes. An ACE isoform is present in large amounts in spermatozoa and is expressed under an alternative, germ cell-specific promoter, whereas ACE present in the seminal fluid is the somatic form of ACE. We have investigated the effect associated with the I/D polymorphism on the level of ACE in seminal fluid and in spermatozoa. No differences in the level of ACE measured in the seminal fluid or in the spermatozoa were associated with the ACE I/D genotypes. We conclude that the modulation of expression associated with the I/D polymorphism is restricted to the somatic ACE promoter. These results also suggest that if one allele modulating the expression of ACE was under positive selection pressure, it was not through an effect on the semen concentration of ACE.