SOME STUDIES ON THE EFFECTS OF ALPHA-CHYMOTRYPSIN ON MAST-CELLS FROM THE RAT AND OTHER SPECIES

We have examined the effect of alpha-chymotrypsin on isolated mast cel ls from different sources. The enzyme induced a dose-dependent secreti on of histamine from purified and non-purified populations of rat peri toneal mast cells. The release was non-cytotoxic and was inhibited by metabolic blockers and extremes of temperature. The process was relati vely slow, being essentially complete within 20 min, and was unaffecte d by phosphatidylserine. A substantial component of the secretion pers isted in the absence of extracellular Ca2+. The release was suppressed by extremes of pH and a variety of anti-allergic compounds and serine esterase inhibitors. In addition to the secretion of preformed mediat ors, alpha-chymotrypsin also induced the metabolism of arachidonic aci d, resulting in the release of prostaglandin D-2 in a dose-related man ner from purified rat peritoneal mast cells. alpha-Chymotrypsin exhibi ted a marked tissue and species selectivity in its action and tissue m ast cells of the rat, guinea pig and human were generally resistant to the enzyme except at cytotoxic concentrations. On the basis of these results, the possible role of endogenous serine esterases in mast cell activation is discussed.