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 cells from different sources. The enzyme induced a dose-dependent secretion of histamine from purified and non-purified populations of rat peritoneal mast cells. The release was non-cytotoxic and was inhibited by metabolic blockers and extremes of temperature. The process was relatively slow, being essentially complete within 20 min, and was unaffected by phosphatidylserine. A substantial component of the secretion persisted 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 mediators, alpha-chymotrypsin also induced the metabolism of arachidonic acid, resulting in the release of prostaglandin D2 in a dose-related manner from purified rat peritoneal mast cells. alpha-Chymotrypsin exhibited a marked tissue and species selectivity in its action and tissue mast 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.