Localization of lectin receptors on bovine epididymal spermatozoa using a colloidal gold technique

Mammalian spermatozoa that leave the testis are neither motile nor fertile. Maturation of spermatozoa occurs during epididymal transport. Among the changes during epididymal passage alterations of the surface properties of spermatozoa appear especially interesting. In this report we describe ultrastructural localization of Con A and WGA-binding sites on bovine spermatozoa from caput and cauda epididymides using a indirect lectin-horse-radish-peroxidase gold technique. With Con A the plasma-membrane covering the sperm head was heavily labelled with gold granules in caput as well as in cauda epididymal spermatozoa. A different distribution was observed for WGA-binding sites. The acrosomal region of caput and cauda spermatozoa was heavily labelled with gold, both in caput and cauda spermatozoa. The postacrosomal region was only sparsely marked in caput sperm whereas in sperm cells originating from the cauda a calix like membrane area displayed intense labelling. Some differences in the number of binding sites were also seen on sperm tails: those of caput spermatozoa show generally more Con A binding sites that those from cauda epididymal spermatozoa. No changes in the number of WGA-binding sites on sperm tails was observed during epididymal passage. The technical aspects of the indirect lectin-horse-radish-peroxidase gold technique are briefly discussed.