RADIOIODINATED PLASMINOGEN - IMAGING AGENT FOR PRE-EXISTING THROMBI

Abstract

Radioiodinated plasminogen was investigated as an agent for localizing preformed thrombi. Canine plasminogen was isolated from fresh plasma by the affinity chromatography technique on a lysine-sepharose 4B column and tagged with 123I or 131I, at < 1 I atom/molecule of enzyme, by the conventional ICl method. When injected into dogs more than 2 days after thrombus induction, radioiodinated plasminogen produced thrombus-to-blood activity ratios of 7.8 .+-. 2.4. Thrombi as old as 6 days was visualized in 80% of the cases. Both the weight of the thrombus and the thrombus-to-blood ratio were more variable for 1 day old thrombi; this may be associated with plasminogen release accompanying thrombus retraction. Radioiodinated plasminogen had potential as an imaging agent for pre-existing thrombi.