Activation of a fibrinolytic system in a dog with mast cell tumor

¹ Veterans Administration Hospital and Meharry Medical College, Nashville, Tennessee

Injection of minute amounts 48/80 (35 µg/kg) into a dog possessing widespread mast cell tumors produced an interesting constellation of biochemical and pharmacological responses on the cardiovascular and hematologic systems. Severe cardiac irregularities and an intense lowering of blood pressure occurred. The most obvious changes which occurred on the blood coagulation system were a lowering of the prothrombin consumption and a prolonged increase in the coagulation time. Of paramount importance, however, was the intense fibrinolytic activity which developed in this animal. This phenomenon was also observed in animals not bearing mast cell tumors but occurred only when very high levels of 48/80 (0.75 mg/kg) were administered. Euglobulin fibrinolytic studies suggest that the observed intense fibrinolytic activity may be partially independent of euglobulin system. Heparin, histamine, and protamine in low concentrations did not activate the fibrinolytic system but produced inhibition in high concentrations (10 µg/ml). Canine mast cell tumors contain considerable esterase and proteolytic activity but there was no obvious evidence of their release into the blood after injection of 48/80 along with histamine, but local proteolytic activation in the mast cell tumor occurred.

Key Words: fibrinolysis • 48/80

Submitted on July 29, 1963