Sperm acrosin activity and fluorescence microscopic assessment of proacrosin/acrosin in ejaculates of infertile and fertile men.

OBJECTIVE

To compare biochemically active with immunoreactive sperm acrosin in fertile and infertile men.

SETTING

This study was conducted in a tertiary care center, the Andrology Clinic, Department of Internal Medicine, University of L'Aquila.

PATIENTS

We evaluated the males in 40 infertile couples with no recognized cause of female infertility and 20 fertile men.

INTERVENTIONS

Ejaculates were collected under standardized conditions of abstinence.

MAIN OUTCOME MEASURES

Total sperm acrosin activity was measured on a spectrophotometer in washed sperm stored at -80 degrees C for 1 to 6 days. The percent of spermatozoa immunostained by an antiserum against proacrosin/acrosin by indirect immunofluorescence (IFL) was determined on methanol fixed sperm smears.

RESULTS

Biochemically active acrosin was correlated to immunoreactive acrosin (P = 0.0028), and both were inversely correlated to the percent of spermatozoa with an abnormal head (P = 0.00024 for acrosin activity and P = 0.0013 for IFL). Biochemically active and immunoreactive acrosin were lower in infertile compared with fertile men (P = 0.0012 and P = 0.0009, respectively). Sixty-eight percent of ejaculates with an acrosin activity lower than the limit value observed in fertile men showed a normal sperm morphology and a normal immunoreactivity for acrosin.

CONCLUSIONS

A low sperm acrosin activity in teratospermic ejaculates is because of a lack or a defect of the immunogenic and functional domains of the protein. A low sperm acrosin in infertile men with normal semen parameters results from a possible functional defect of the enzyme that is immunohistochemically detected in spermatozoa.