Fibrinolytic enzyme in tracheobronchial secretion of rats: existence of plasminogen activator.

It is known that a plasminogen activator exists in the secretion of various organs, i.e., the existence of plasminogen activator in milk, tears, saliva, seminal fluids, urine and bile has been already demonstrated. However, the existence of the fibrinolytic enzyme in tracheobronchial secretions has not been known until this time. We found a new method to collect the tracheobronchial secretion of rats, and succeeded in detecting the fibrinolytic activity in the tracheobronchial secretions. Furthermore, it was found that the substance exhibiting the fibrinolytic activity in this secretion was not protease but plasminogen activator. In addition, some chemical properties of this plasminogen activator are presented, and the physiological and pathophysiological significances of it are discussed in this paper.