Differences in concanavalin A-FITC binding to rat spermatozoa during epididymal maturation and capacitation

Rat spermatozoa from the caput epididymis and cauda epididymis, but not from the testis, demonstrated a crescent of greenish fluorescence on the convex surface of the sperm head, as observed by fluorescence microscopy after staining with concanavalin A-fluorescein isothiocyanate. The percentage of spermatozoa displaying this fluorescent zone decreased during incubation under capacitating conditions, both in vivo and in vitro, suggesting that a glycoprotein zone that is capable of binding concanavalin A was removed or altered during the capacitation period.