Functional comparison of annexin V analogues labeled indirectly and directly with iodine-124

We are interested in imaging cell death in vivo using annexin V radiolabeled with I-124. In this study, [I-124]4IB-annexin V and [I-124]4IB-ovalbumin were made using [I-124]N-hydroxysuccinimdyl-4-iodobenzoate prepared by iododestannylation of N-hydroxysuccimmidyl-4-(ttributystannyl)benzoate. [I-124]4IB-annexin V binds to phosphatidylserine-coated microliter plates and apoptotic Jurkat cells and accumulates in hepatic apoptotic lesions in mice treated with anti-Fas antibody, while [I-124]4IB-ovalbumin does not. In comparison with I-124-annexin V,[I-124]4IB-annexin V has a higher rate of binding to phospliatidylserine in vitro, a higher kidney and urine uptake, a lower thyroid and stomach content uptake, greater plasma stability and a lower rate of plasma clearance. Binding of radioactivity to apoptotic cells relative to normal cells in vitro and in vivo appears to be lower for[I-124]4IB-annexin V than for I-124-annexin V.