An in vivo evaluation of ^*I-fibrinogen labeled by four different methods

The thrombus uptake of radioiodinated fibrinogen prepared by either the iodine monochloride, chloramine-T, electrolytic, or enzymatic method was compared in dogs using a surgical model of venous thrombosis. The labeled fibrinogen uptake into thrombi was measured by external scintillation counting in vivo and in vitro determination of thrombus-to-blood ratios. The iodine monochloride preparations resulted in the greatest fibrinogen uptake and the highest thrombus-to-blood ratios. The uptake of enzymatically labeled fibrinogen most closely approached that of the iodine monochloride preparations. The chloramine-T and electrolytic preparations of fibrinogen were less satisfactory since these methods either alter the fibrinogen or produce unstable labeling of the fibrinogen.