Phenotypic expression of mast cell granule proteinases. Distribution of mast cell proteinases I and II in the rat digestive system.

The distribution of mast cell granule proteinases in the rat digestive system was determined immunohistochemically. The population of toluidine blue-staining mast cells was accounted for by cells containing either rat mast cell proteinase I (RMCPI) or rat mast cell proteinase II (RMCPII). Granules in greater than 90% of RMCPI-containing cells stained red after the Alcian blue/safranin sequence, whereas all RMCPII-containing mast cells stained blue. The red/RMCPI phenotype was typical of the connective tissue mast cells (CTMC) that populate the proximal, non-mucosal, regions of the digestive system, and was also abundant in the serosa and in rectal and gastric muscularis. The blue/RMCPII phenotype, absent from non-mucosal sites except for rare cells in intestinal submucosa and muscularis, predominated in all mucosal tissues and resembled mucosal mast cells (MMC). A third, minor population of cells containing RMCPI but staining blue in the Alcian blue/safranin sequence was detected in both non-mucosal and mucosal tissues. Blue/RMCPI mast cells were rare in the small intestine but more frequent in the mucosa of the stomach and large intestine and in the connective tissues. It is suggested that granule proteinase phenotyping may provide an alternative technique in the analysis of mast cell heterogeneity.