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An ultrastructural analysis of lectin receptors on the submandibular glands from mice of both sexes was performed utilizing horseradish peroxidase-labelled lectins in conjunction with antiperoxidase antibody and protein A-gold. Both qualitative and quantitative sex-related differences in terminal sugar expression within secretory granules were detected. Following sialidase digestion, also subterminal acceptor sugars for terminal sialic acids, proved to be differentially expressed in the submandibular glands of males and females. Heterogeneous distribution of sialoglycoconjugates characterized by the terminal disaccharide sialic acid-beta-galactose was found to occur in female acinar cells. Also DBA reactive sites indicating the presence of terminal alpha-N-acetylgalactosamine discriminated between male and female acinar secretory glycoconjugates. This difference was emphasized by sialidase pretreatment that evidenced a marked occurrence of sialic acid subtended to alpha-N-acetylgalactosamine in males in contrast to a modest presence in females. The different sialylation patterns of acinar cell secretory products, probably related to a different expression of O- and N-linked sialoglycoconjugates, give insight into the sexual dimorphism of the mouse submandibular gland known until recently for the convoluted granular tubules.

Sites of binding of eight different lectins (LTA, UEA I, WGA, SBA, DBA, CON A, PNA, RCA I) to cat submandibular gland were studied after exposure of tissue sections to sialidase, alpha-fucosidase, beta-galactosidase, alpha-mannosidase, beta-N-acetylglucosaminidase. All lectins were affected by enzymatic predigestion and the labeling of individual lectins was highly dependent upon the glycosidase used to pretreat the sections. Glycoconjugates of demilunar, acinar and ductal cells exhibited a different composition of terminal sequences. For example, fucose proved to form the disaccharide fucose-galactose in demilunar and acinar cells, whereas it was present with the sequence fucose-N-acetyl-D-glucosamine in striated duct cells. Sialic acid participated both to the terminal sequence sialic acid-galactose and sialic acid-N-acetyl-D-galactosamine either in demilunar or in ductal cells. Lectin labeling combined with glycosidase digestion was also helpful in verifying the influence of neighbouring oligosaccharides on the affinity of lectins for the respective sugars.

In order to verify the influence of fixative on the formation of any nonspecific lectin bindings, the authors have carried out an investigation on rabbit salivary glands. The results obtained applying peanut, soybean, wheat germ, and winged pea lectins to unfixed samples of rabbit submandibular and sublingual glands agreed almost completely with the results of our previous research effected on the same samples fixed with aldehydes. The most important differences between the fixed samples and the unfixed ones consisted in the lack of reactivity of the material inside the secretion lumina to all the lectins used, and in the lack of peanut binding to the submandibular gland. No significant differences in intensity and location were found for soybean, wheat germ, and winged pea lectins.

The glycosidic residues in the submandibular gland of cat at different ages were studied using a battery of 6 lectins conjugated with horseradish peroxidase as histochemical reagents. The submandibular glands of sucking and adult cats showed diversities in the reaction intensity or in the localization of binding sites. The morphologically distinct secretory tracts appear to produce different types of oligosaccharides in sucking and adult subjects. The sugars that can be defined as growth markers in the cat submandibular gland seem to be alpha-L-fucose, N-acetyl-D-glycosamine and beta-galactose. The data originated from this research have been compared with biochemical data previously obtained by the authors on the cat submandibular gland during growth.