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.