Acid mucopolysaccharides in mast cell granules were histochemically studied in the lesion of urticaria pigmentosa and in the dermis of normal human skin. Alcian blue and azure A were used to stain mucopolysaccharides. Bromphenol blue was employed for detection of basic proteins.In a further attempt to identify various polyanions, staining was carried out with alcian blue containing various concentrations of electrolytes. Methylation, saponification, and digestion with streptomyces or testicular hyaluronidase, chondroitinase ABC, sialidase, or desoxyribonuclease were also employed.The results obtained are most likely to suggest the presence of hyaluronic acid in mast cell granules. human dermis; mast cell; hyaluronic acid Mast cells were first described by Paul Ehrlich in 1879. At that time he called attention to the affinity of the granules in these cells for _basic dyes. Anionic groups in mast cell granules have the capacity to shift the absorption spectrum of certain basic dyes in dilute acidic solutions, resulting in a metachromatic effect. This characteristic still serves as the basis of their identification.Many biochemical and histochemical studies indicated the presence of sulfated and non-sulfated acid mucopolysaccharides in the granules. Acid mucopolysac charides in question are heparin, chondroitin sulfates and hyaluronic acid. The presence of hyaluronic acid in mast cell granules was suggested for the first time by Asboe-Hansen (1950) based on the finding of large numbers of mast cells in tissues rich in hyaluronic acid, such as the synovia of joints, and on the accumulation of mast cells following the enzymatic breakdown of tissue hyaluronic acid. The effect of hyaluronidase treatment on the metachromatic staining of mast cell granules has been claimed as evidence both for and against their containing hyaluronic acid. Velican and Velican (1959), after studying the effect of hyaluronidase on the metachromatic staining of mast cells in autopsy specimens of human bronchial lymph nodes, concluded that the metachromatic substance in some of the granules consists exclusively of hyaluronic acid. Similar results were observed by Bensley (1950), and others. On the other hand, West (1958) pointed out that hyaluronidase did not destroy the metachromasia of mast cell granules,
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