Histoenzymological detection of sialic acids in the rodent salivary glands

Sections from the major salivary glands of rats and mice were used to locate, characterize and compare sialoglycoconjugates by means of lectin histochemistry, sialidase digestion, periodate oxidation and potassium hydroxide deacetylation. The gland sialylated macromolecules contained the terminal dimers sialic acid-beta-galactose and sialic acid-alpha-N-acetyl-galactosamine but differed in the varieties of sialic acids and the linkages of sialic acids to penultimate sugars. Indeed, the submandibular and parotid glands exhibited a notable occurrence of periodate labile sialic acids with C7 and/or C8 and/or C9 acetyl groups in their polyhydroxyl chains. In particular, C9 acetylated sialic acids were mostly linked alpha 2-6 to beta-galactose. The sublingual glands, instead, were strongly characterized by a presence of C9 acetylated sialic acids bound alpha 2-3 to beta-galactose. Also, sialic acids with O-acetyl substituents at C4 were evident in the mouse parotid gland and in the rat submandibular and sublingual glands. The great variety of sialoderivatives expressed by the rodent salivary glands was correlated with the differential involvement of these compounds in lubricating and defensive processes. Sex-related differences regarding the sialic acid location, acetylation degree and linkage were shown in the submandibular glands of both species