title: Selective antigen-stimulated release of proteolytic activity from rat mast cells.
abstract: Stimulation of rat mast cell suspension from actively sensitized rats with antigen in vitro produced a parallel release of histamine and enzyme, probably proteolytic activity, which releases p-nitrophenol from an L-tyrosine-p-nitrophenyl ester derivative (TPNE). The histamine and enzyme release correlated with respect to their dependence on antigen concentration, reaction time and inhibition by 2,4-DNP and papaverine. In contrast, more than 50% of total histamine but nearly no enzyme was released by the ionophore A 23.187 and C 48/80 (each less than or equal to 1 microgram/ml). The enzyme was apparently secreted predominantly in a particular form. It was approximately 50% inactivated by heating for 1 h at 56 degree C or by incubation for 3 h at 37 degrees C with the chymotrypsin inactivator tosyl-phenylalanine chloromethylketone (TPCK; 2.5 X 10-4 M) or for 5 min at 37 degrees C with benzyl sulphonyl fluoride (2.5 X10-4 M), which reacts with SH groups. Heating for 3 min at 100 degrees C destroyed it completely. On the basis of these properties we suggest that the antigen released enzyme is the known granulabound chymase from rat mast cells. TPNE was not only a cleavable substrate for the enzymatic activity in the 800 g cell supernatant following antigen stimulation, but also a strong inhibitor of the histamine release on administration before antigen (IC50 approximately 10-6 M). It appears that the same enzyme activity acts initially intracellularly as activator of the histamine secretion and then is subsequently released along with histamine as a further mediator. Extracellularly this enzyme may act as a modulator of inflammatory reactions in type I allergy both locally and systemically.
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology*; D000001:Calcimycin / Q000494:pharmacology; D006636:Histamine Release / Q000187:drug effects; D066298:In Vitro Techniques; D008407:Mast Cells / Q000201:enzymology*; D010447:Peptide Hydrolases / Q000378:metabolism*; D051381:Rats; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
chemical_list: D000941:Antigens; D000001:Calcimycin; D003189:p-Methoxy-N-methylphenethylamine; D010447:Peptide Hydrolases