Fibrinolytic activity of human tissues and dog mast cell tumors.

Since Erhlich" discovered the mast cell, much has been written concerning its morphology, distribution, and chemical composition. There is now rather convincing evidence that the mast cell, like the platelet, is a storehouse of pharmacologically important substances (histamine, heparin, and possibly hyaluronic acid). The mast'cells of some species have also been reported to contain 5-hydroxytryptamine. Undoubtedly, there are probably other important substances that remain to be discovered in this unusual cell. While investigating the fibrinolysis of tissues we observed considerable lytic activity in the spleen of a patient with splenic mastocytosis. We later encountered a similar substance in mast cell tumors of a dog. Recently, Benditt and Arase 8 described appreciable quantities of an unidentified proteolytic enzyme in mast cells. According to these workers, the enzyme possesses properties similar to that of the alpha chymotrypsin enzyme. This unique proteolytic activity of the mast cell and our findings mentioned above prompted an investigation of the fibrinolysis of various tissues that have been demonstrated to contain large numbers of mast cells. To our knowledge, there are no reports in the literature dealing with the fibrinolytic properties of this cell.