The histochemical demonstration of protein in epithelial mucins *, †

SYNOPSIS Although the saccharide side chains of epithelial mucins in situ (presumably glycoproteins) can be readily stained, it is difficult to demonstrate the protein core of such mucins histochemically, even following attempts to remove the saccharide residues by various chemical and enzymatic treatments. A protein presumed to be extrinsic to the mucin may be demonstrated directly, under certain circumstances, by the acid dye Biebrich scarlet and indirectly by the increase in basophilia following brief proteolysis. Thiol and disulphide groups in mucins may be demonstrated by both direct and indirect techniques.