The influence of coumarin on tissue levels of radio-labelled plasma protein and povidone (polyvinylpyrrolidine) in normal and thermally injured rats.

1. The administration of coumarin resulted in a two-fold increase in the entry of 51Cr-labelled rat plasma protein into otherwise normal tissues. 2. Prior treatment of rats with coumarin allowed about 50% more radio-labelled protein to enter the tissues immediately after thermal injury than occurred with thermal injury in untreated rats. 3. In coumarin-treated rats, 30 min or more after thermal injury, tissue levels of 125I-labelled povidone (polyvinylpyrrolidine) were significantly elevated or showed no change compared with tissue levels in rats which received only thermal injury. 4. Conversely, tissue levels or radio-labelled protein in coumarin-treated rats, 30 min or more after thermal injury were significantly reduced to between 20 and 30% of those in untreated, thermally injured rats. 5. These results were attributed to enhanced proteolysis of the radio-labelled protein caused by coumarin. Other results have shown that normal protein is similarly affected. 6. The products of proteolysis may then rapidly leave the tissues, freeing the osmotically-held fluids and reducing the oedema.