Serum and urinary fibrinolytic activity related to the hemorrhagic diathesis in irradiated dogs.

The urine and serum fibrinolytic activity were measured in dogs following whole body radiation ranging from 450 to 800 r generated by 1,000 kv. and 250 kv. machines. The fibrinolytic activity of the urine showed a precipitate rise 4 to 5 days before death in all dogs with pulmonary hemorrhage as the main cause of death. The fibrinolytic activity of the serum showed a similar rise, which was most pronounced in the case of those animals which did not survive. The fibrinolytic activities of the urine and serum approached control levels at about the 24th day after irradiation in all the surviving dogs. The possible mode of activation of the fibrinolytic enzyme in vivo is discussed and approaches to prevention of the hemorrhagic syndrome are suggested.