Continued incorporation of circulating radiolabeled fibrinogen into preformed coronary artery thrombi.

This study measured the growth over time of experimental coronary artery (CA) thrombi by radiolabeled fibrinogen uptake. 125I-fibrinogen was injected into dogs and 24 hours later CA thrombi were induced by electrical current. Twenty-four hours after CA thrombus induction, 131I-albumin (group A) or 131I-fibrinogen (group B) was injected. At 48 hours after thrombi induction, the thrombi were removed, divided into segments, and their radioactivity measured. The 131I-fibrinogen in the group B thrombi was significantly greater than the 131I-albumin in group A thrombi (P less than 0.001). In further studies, the 131I-fibrinogen was given 48 and 72 hours post CA thrombus formation. Significant 131I was also found in these CA thrombi. 125I-fibrinogen and 131I-fibrinogen incorporation occurred in virtually all segments of the thrombi. The results suggest 1) CA thrombi growth continues for at least 72 hours after initial formation; 2) the presence of 131I in the thrombi was due to gradual fibrin deposition throughout the thrombus.