Human sperm endothelial nitric oxide synthase expression: correlation withsperm motility

Objective: To characterize the pattern of endothelial nitric oxide synthase (eNOS) expression on human spermatozoa and to determine whether sperm eNOS expression correlates with sperm function. Design: Prospective, observational study. Setting: University infertility clinic. Patient(s): Twelve nonazoospermic infertile men. Intervention(s): Semen samples (n = 12) obtained from nonazoospermic infert ile men were fractionated on discontinuous Percoll gradients. Endothelial n itric oxide synthase staining on spermatozoa was correlated with sperm moti lity in Percoll gradient-fractionated spermatozoa. Endothelial nitric oxide synthase protein was detected with the use of a previously characterized m onoclonal antibody. Control slides were incubated with preabsorbed antibody or mouse immunoglobulin G. Main Outcome Measure(s): Localization of eNOS on human spermatozoa and corr elation between the pattern of sperm eNOS expression and sperm motility. Result(s): Morphologically normal spermatozoa exhibited postacrosomal and e quatorial eNOS immunostaining. However, abnormally shaped spermatozoa often exhibited aberrant staining tin the midpiece and/or head region). A signif icant negative correlation was observed between the percentage of sperm wit h aberrant eNOS immunostaining and the percentage of motile sperm ((r) over bar = -.46). Conclusion(s): The specific localization of eNOS to human spermatozoa sugge sts that nitric oxide may be involved in normal sperm physiology. However, aberrant patterns of sperm eNOS expression are associated with decreased sp erm motility, possibly through the generation of excessive cytotoxic oxidan ts. (Fertil Steril(R) 1998;70:1143-7. (C) 1998 by American Society for Repr oductive Medicine.).