Release of soluble tryptase but only minor amounts of chymase activity from cutaneous mast cells

Tryptase and chymase are the major serine proteinases of skin mast cells bu t their biologic significance depends on their activity. In this study, we demonstrate the release of soluble activity of tryptase, but not markedly t hat of chymase, into skin blister fluids induced by freezing with liquid ni trogen as well as into supernatant during incubation of 8 whole skin specim ens with compound 48/80 for up to 2 days followed by sonication. Incubation of 3 other skin specimens in compound 48/80 for up to 2 days revealed that the number of mast cells displaying tryptase activity decreased significan tly on day 2, and the number of mast cells showing chymase activity (but no t those showing chymase immunoreactivity) decreased significantly on day I but not thereafter on day 2. The results of 3 skin organ cultures for up to 14 days showed steady decrease in the number of tryptase-positive cells bu t persistence of mast cells containing chymase activity. Chymase in solutio n was sensitively inhibited by 0.01 mg/ml alpha (1)-antichymotrypsin but hi gher concentrations (0.3-3.0 mg/ml) were needed for inhibiting chymase on s kin sections. In conclusion, after mast cell degranulation tryptase activit y is substantially solubilized and it may potentially affect both local and distant skin structures. Instead, chymase is partially inactivated and the remaining chymase activity persists at the site of degranulation having on ly local effects.