Changes in oocyte plasma membrane binding sites on boar spermatozoa with capacitation and acrosome reactions

The objective of this study was to determine the localization and distribution of oocyte plasma membrane binding sites on capacitated and acrosome-reacting live boar spermatozoa. Localization of oocyte plasma membrane binding sites on boar spermatozoa was determined with fluorescence microscopy and population distribution was examined with flow cytometry. The number of spermatozoa with oocyte plasma membrane bound to the equatorial segment and postacrosomal region of the sperm head significantly increased with capacitation. Equatorial segment labelling further increased with induced acrosome reactions. When the population distribution of oocyte plasma membrane binding sites on live boar spermatozoa was analysed, the percentage of spermatozoa with bound oocyte plasma membrane significantly increased after capacitation compared with that of washed spermatozoa. Binding of oocyte plasma membrane did not increase in control spermatozoa incubated under non-capacitating conditions and was not correlated with the percentage of dead spermatozoa. A change in localization of oocyte plasma membrane binding sites on the sperm head was demonstrated using fluorescence microscopy and an increase in oocyte plasma membrane binding sites after capacitation was shown using flow cytometry.