Impaired hamster egg penetration by human sperm from ejaculates with low acrosin activity but otherwise normal.

Objective: To determine if a low acrosin activity in otherwise normal ejaculate from infertile patients is associated with an impairment of sperm functions involved in the hamster egg penetration.

Setting: A tertiary care center, the Andrology Clinic, Department of Internal Medicine, University of L'Aquila.

Patients: Nine infertile patients with low acrosin activity in otherwise normal ejaculate (including normal immunoreactivity for acrosin) were studied; nine fertile men served as a control group. The two groups were homogeneous for seminal parameters.

Interventions: The hamster egg penetration assay and the acrosome reaction rate assessment were performed on capacitated sperm suspensions in basal conditions and after ionophore challenge.

Main Outcome Measures: The penetration rate, the penetration index, and the acrosome reaction rate were measured and compared between the groups.

Results: No penetration was achieved in seven patients and a low penetration was achieved in two cases. The difference with the control group was significant. The ionophore challenge was associated to penetration of hamster eggs in seven of nine patients, but the penetration index was significantly lower than the controls. Acrosin activity was correlated to hamster egg penetration. Both spontaneous and induced acrosome reaction rate were similar in the two groups.

Conclusions: A low sperm acrosin activity in otherwise normal ejaculate is associated with an impaired hamster egg penetration. This impairment does not seem to be due to altered dynamics of acrosome reaction.