Interference in localization of I131 fibrinogen in rat tumors by anticoagulants

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Abstract
A transplantable tumor of the rat, the Murphy-Sturm lymphosarcoma, was found to contain 15–25% of the administered radioactive dose 18 hr after intravenous injection of I131-labeled rat fibrinogen in a rat bearing a tumor in the 2–12 g wt. range. At this time the concentration of radioactivity per gram of tumor was found to be some 4–15 times that of such vascular organs as the liver and kidney, smaller tumors (2–5 g) localizing much more of the injected radioactive dose per gram than larger tumors (8–12 g). These tumors did not concentrate radioactivity after intravenous injection of either I131 γ-globulin or inorganic NaI131. The administration of heparin or warfarin in dosages adequate to completely inhibit the blood coagulation mechanism throughout the 18-hr experimental period decreased this specific tumor localization of I131 fibrinogen by 60–80%. It is concluded that the effect of heparin and warfarin on the coagulation mechanism is probably responsible for this decrease. A possible mechanism of tumor localization of I131 fibrinogen is discussed.