Studies on Proteolytic, Fibrinolytic, Antitryptic and Antifibrinolytic Activities in the Blood of Rats

Abstract

No change in proteolytic activity could be demonstrated in the serum of rats in "tourniquet shock, " using the degree of liberation of tyrosine-tryptophan from a casein substrate as an index of proteolytic activity. The antitryptic titer in the same animals, measured on crystalline trypsin with casein as a substrate, was slightly lowered, compared to normal. Comparison of the fibrinogenolytic and proteolytic activities of trypsin, plasmin and the chloroform-activated serum enzyme indicated parallelism between these enzymes. This similarity further substantiates the claim that plasmin can act as a proteolytic enzyme and may well play a significant role in the process of protein breakdown. It was not feasible to use the destruction of the clotting ability of fibrinogen as a test method for fibrinolytic activity in blood of rats, subjected to "tourniquet shock." Fibrinolytic activity and reduced antifibrinolytic activity could be demonstrated in the plasma of rats in "tourniquet shock" and after epinephrine admn. to normal rats. The fibrinolytic activity observed may be due either to an actual decrease in the plasmin inhibitor concn. or to an augmentation of the plasmin content. The recognition of plasmin and plasmin inhibitor as balancing components of a proteolytic system existing in normal blood greatly facilitates an approach to the problem of the mechanism of protein breakdown.