The role of chymotrypsin-like protease of rat mast cells in inflammatory vasopermeability and fibrinolysis.

The isolated chymotrypsin-like protease of rat mast cells was shown to cause an increase of vascular permeability in rat skin. Inactivation of the enzymatic activity of the cationic protease abolished the vasoactivity. The smallest effective dose of the maximally active enzyme was estimated to be 0.5 micrograms per injection site, which is less than the amount of the endogenous mast cell enzyme in areas of skin similar to that of an injection site. The smallest effective dose for bovine trypsin was similarly estimated to be 0.3 micrograms per injection site, which is in good agreement with the values previously reported by others. The results suggest that the mast cell protease may act as a mediator of inflammatory vasopermeability. The effect of the enzyme on two potential biological substrates was tested. The enzyme does not hydrolyze elastin, but degrades fibrin clot.