BIOCHEMICAL AND HISTOCHEMICAL IDENTIFICATION OF SIALIC ACID CONTAINING MUCINS OF RODENT VAGINA AND SALIVARY GLANDS

The mucins elaborated in the mucification reaction of the vagina of the rat and mouse, like salivary mucins, show the histochemical properties of a nonsulfated acid mucopolysaccharide. In the mouse these have been identified as sialomucins on tile basis of the elimination of basophilia from tissue sections by specific digestion with purified sialidase. However, the removal of sialic acid effected by sialidase is not accompanied by an alteration in periodic acid Schiff staining and hence extensive degradation of the polymer does not take place. Sialidase alters the staining of mouse sialomucins quickly in the sublingual gland, relatively slowly in the vagina and even more slowly in the submaxillary gland. Digestion with the enzyme fails to alter staining reactions in the siahic acid-rich, histochemically similar mucin in the salivary gland and vagina of the pregnant rat, and fails to release sialic acid either from histologic sections or homogenates of these rat organs. Changes in the sialic acid level in the vagina during the oestrous cycle parallel the cyclic variations of the amount of mucin observed histochemically. Both are consistently elevated in pregnancy. The sialic acid concentration is low and mucin is absent in oestradiol treated pre-ovulatory mice, but these increase with subsequent progesterone treatment. Identification of the sialic acid by means of paper chromatography reveals that the rat and mouse vagina and sublingual and submaxillary glands all contain N-acetylneuraminie acid and that mouse vagina and rat submaxillary gland also contain N-glycolylneuraminic acid. An un-identified form of neuraminic acid with rapid mobility in two solvents is present in the rat submaxillary gland.