Selected sperm differ from nonselected cells in their electrophoretic mobility (EPM) after demembranation

Human semen samples were first treated by swim-up migration or by Percoll density gradient centrifugation for selection of spermatozoa. The net surface charges of spermatozoa in the resulting compartments were indirectly evaluated by the electrophoretic mobility (EPM) during spermatozoal microelectrophoresis. Significantly different electrophoretic mobilities were measured between the compartments after demembranation with 0.1% (v/v) Triton X-100. However, without intermediate treatment by the detergent no significant differences were detected between the spermatozoal EPM. In addition, spermatozoa were divided into migrated and nonmigrated spermatozoal populations by the swim-up technique, and then treated with urea to remove spermatozoal coats. No significant differences in EPM were detected between these two groups. This investigation demonstrates that selected spermatozoa from semen exhibit an additional dimension of superiority, in EPM, to nonselected spermatozoa, which may better equip them for the process of fertilization. Measurements of EPM, therefore, may provide yet another, perhaps valid, means of developing a clinical tool for evaluating the potential fertilizing capacity of a semen sample in infertility studies.