A semiquantitative immunohistochemical technique for the detection of N‐acetyl α‐D‐neuraminic acid, N‐acetyl β‐D‐glucosamine and its β‐(1 ŕ 4)‐linked internal chains, α‐D‐glucopyranosyl and α‐D‐mannopyranosyl and its α‐(1 ŕ 2)‐linked internal chains and sterically related, nonreducing, end‐chain residues of oligosaccharide chains of glycoproteins or glycolipids on the surface of membranes was developed using Con A and wheat germ lectins.When this method was applied to the localization of carbohydrate receptors on the membrane of the normal human spermatozoa, it was found that the Con A and wheat germ lectin receptors were mainly located in the equatorial and post nuclear cap with few receptors located in the acrosome and neck. None of them were found in the intermediate segment plus tail.Con A receptors were α‐D‐mannopyranosyl end‐chain residues and wheat germ lectin receptors were N‐acetyl β‐D‐glucosamine (1 ŕ 4)‐linked internal chains. These groups occur together in the oligomannosidic type of N‐glycosidic‐linked oligosaccharide chains of glycoproteins and so the use of both lectins on desialycated membranes or on those which contain nonclustered N‐acetyl neuraminic acid residues may be of help to localize this type of glycoprotein oligosaccharide chains.Con A receptors were not removed after proteases digestion, suggesting the possibility that they are part of intrinsic spermatozoal antigens.

Peroxidases have been detected in the membrane of the ejaculated normal spermatozoon; their distribution on the different zones of the gamete has been determined. This distribution is similar to that of the N-linked glycoprotein-containing oligosaccharides. Their resemblance and similarity to the plant peroxidases, which are glycoproteins with N-type oligosaccharides, suggest that the sperm peroxidases might be, at least partially, identical to concanavalin A (Con A) and wheat germ lectin glycoprotein-containing receptors.

Autoproteolysis of human spermatozoa produces oligopeptides with oligosaccharide chains of the N-glycosidic-linked type that are released from the "surface exposed" parts of glycoproteins. The products eluted in the previous washing of the spermatozoa have the same composition and solubility characteristics as the oligopeptides from the digestion. This suggests that autoproteolysis is a constant process that normally occurs on the spermatozoa membrane. The cytochemical characterization and localization of the N-glycosidic-linked oligosaccharide receptors on the human spermatozoa membrane after digestion, in the presence or absence of seminal plasma, indicates that only part of the oligosaccharides are cleaved. Their distribution on the different zones of the spermatozoon changed as the probability of detecting these receptors in the intermediate segment increased after proteolysis; this indicates that in this zone the receptors are cryptic ones that become exposed by the action of the proteolytic enzymes. In the presence of seminal plasma most receptors on the acrosome are eliminated.

Similar locations of the Con A and wheat germ lectin receptors were obtained by using fluorescent lectins, in nonfixed spermatozoa and in spermatozoa fixed with formaldehyde and methanol, showing that in samples with the same previous treatment, worked out by the same operator, in which enough determinations have been performed to eliminate individual variations, the different procedures of fixation produced similar results. The locatizations obtained with fluorescent lectins confirm previous results, produced with the peroxidase technique, indicating that the lectins interact with oligomannosidic oligosaccharide receptors situated mainly in the equatorial segment of the acrosome and postnuclear cap. They also indicate the presence of similar receptors that were not detected previously on the neck and intermediate segment. The larger size of the lectin-peroxidase-diaminebenzidine reagent compared to that of the fluorescent lectins suggests that the new receptors are semicriptic and were not detected by steric effects in the first case, but were able to interact with lower volume, fluorescent probes. It is suggested that these oligomannosidic chains could be recognition signals for the elimination of incompetent sperm during their passage through the female reproductive track. Also these oligosaccharides and its possible metabolic variations could be involved in the interaction between the acrosome-reacted spermatozoa with the zone pellucida.

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