Sperm-zona pellucida binding of human sperm is correlated with the immunocytochemical presence of proacrosin and acrosin in the sperm heads but not with the proteolytic activity of acrosin

To determine whether the sperm-zona pellucida (ZP) binding is related to the presence of immunoreactivity for proacrosin and acrosin and/or to the proteolytic activity of acrosin. The Andrology Clinic, University of L’Aquila, Italy. Thirty-five infertile couples and 15 men of proven fertility. Salt-stored unfertilized oocytes after IVF were inseminated with a mixture of equal numbers of test and fertile donor sperm after swim-up selection, respectively labeled with fluorescein or rhodamine. Total acrosin activity, the percent of sperm immunostained for proacrosin and acrosin, and the percent of sperm with oval heads were evaluated in fresh semen and after swim-up selection. Three zonae were used for each patient and sperm-ZP binding ratio (ZP ratio) was calculated as the total number of test sperm bound to ZP divided by the total number of control sperm bound to ZP. The ZP ratio was compared with the percent of live sperm immunostained for proacrosin and acrosin, with total acrosin activity and with the percent of sperm with oval heads after swim-up selection. The sperm-ZP binding ratio was correlated positively with the percent of sperm immunostained for proacrosin and acrosin and with the percent of sperm with oval heads, but not with acrosin activity. Ejaculates with immunostaining for proacrosin and acrosin≥55% of sperm (the mean value of infertile couples) and acrosin activity