Demonstration of antiinflammatory activity of fibrinogen and fibrinopeptides in rats.

Carrageenin-induced inflammatory rat paw swelling was significantly inhibited by intraperitoneal injection of rat fibrinogen. Whole-body radioscanning of the rat after intraperitoneal administration of 131I-labeled fibrinogen revealed the accumulation of radiolabeled material in the inflammed rat paw. Resorption studies showed that not more than 4% of the intraperitoneally administered [125I] fibrinogen could be demonstrated in the peripheral blood. Furthermore only 1/3 of this circulating radiolabeled protein was able to take part in clot formation, suggesting that inhibition of edema formation is mediated by fibrinogen-derived split products. This is further supported by the finding that rat fibrinopeptides, released by the action of thrombin, also diminish edema formation both after intracardial and intraperitoneal injection into carrageenin-stimulated rats.