HISTOCHEMISTRY AND MORPHOLOGY OF PORCINE MAST-CELLS

Mast cells have been described extensively in rodents and humans but n ot in pigs, and the objective of this study was to characterize porcin e mast cells by histochemistry and electron microscopy. Carnoy's fluid proved to be a good fixative but fixation with neutral buffered forma lin blocked staining of most mast cells. Alcian Blue stained more mast cells than did Toluidine Blue (pH 0.5), although Alcian Blue also sta ined goblet cells. In pigs, unlike rodents, the Alcian Blue method did not distinguish between mast cells in the intestinal mucosa and those in the connective tissue of the intestinal submucosa, tongue and skin . Mast cells were significantly larger in adult pigs than in piglets; in adult pigs and piglets, mast cells in the intestinal mucosa were si gnificantly larger than those in submucosal connective tissue, and the y were more varied in shape in piglets and adults. Granules in mast ce lls in the intestinal mucosa stained less intensely than those in mast cells in connective tissue of tongue, skin and intestinal submucosa. Mast cells in the connective tissue of the tongue, skin and intestinal submucosa fluoresced strongly when stained with berberine sulphate or with a mixture of berberine sulphate and Acridine Orange, but mast ce lls in the intestinal mucosa did not. All mast cells reacted positivel y in an enzyme-histochemical method previously used to detect human tr yptase but not in a method previously used to detect human chymase. Ma st cells in the medulla of thymus stained similarly to mast cells in t he intestinal mucosa. Ultrastructural differences between mast cells w ere not detected.