Localization of wheat germ agglutinin lectin receptors on human sperm by fluorescence microscopy: Utilization of different fixatives
Wheat germ agglutinin (WGA) and Concanavalin A (Con A) seem to be the most widely studied of the lectins used to investigate sperm surface receptors. It has been reported that WGA receptors on human sperm membranes may be closely related to male fertility and that WGA receptor deficiency may cause human infertility. Although these claims may not be negated, there are many discrepancies in current literature regarding the localization and detection of human sperm WGA receptors. These discrepancies are probably the result of variations in the pretreatment of sperm before fixation and sperm-lectin interaction. This study investigated the effect of different fixation procedures on the localization of human sperm WGA receptors on normal spermatozoa. Comparative studies were performed on spermatozoa separated by wash-swim-up and fixed with 4% formaldehyde, 95% ethanol, or Bouin's solution, or nonfixed (air-dried) using fluorescein isothiocyanate-conjugated WGA. There were significant differences (p <.01) in the % WGA receptor localization following the different fixation procedures on samples receiving the same treatment previous to fixation. The different fixatives affect the plasma membrane to different degrees, resulting in an alteration of lectin receptor localization. To allow a better comparison and understanding of results, a standardized preparation procedure is recommended during studies using lectins as molecular probes. The results suggest than an aldehyde fixative may be the fixative of choice for sperm membrane studies.