Demonstration of chymotryptic and tryptic activities in mast cells of rodents: Comparison of 17 species of the family muridae

On the basis of studies in laboratory rats, mast cells were originally clas sified into two subgroups, namely, mucosal mast cells (MMCs), which contain ed chymase, and connective tissue mast cells (CTMCs), which contained both tryptase and chymase. This classification has been applied to other animal species, despite the fact that the MMCs and CTMCs of such species sometimes consist of mixed populations of mast cells in terms of tryptase and chymas e constitution. This report describes the protease constitution of mast cells in 17 species of nine genera (Acomys, Apodemus, Cricetulus, Meriones, Millardia, Mus, Ra ttus, Sigmodon and Vandeleuria) of the family Muridae. MMCs with negative t ryptase activity were detected only in the intestinal mucosa of six subspec ies of Mus musculus, two Rattus spp. and Vandeleuria oleacea, and only Apod emus sylvaticus possessed CTMCs with no tryptase activity. Since mast cells conforming to the conventional classification were observed only in three of the nine genera examined, we propose that mast cells of rodents of the f amily Muridae should be classified by their protease constitution rather th an by their location. (C) 2001 Harcourt Publishers Ltd.