Synthesis and tissue distribution study of iodine-labeled benzyl- and xylylamines

Four iodine-125 labeled mono- and diamines were prepared and evaluated as potential brain-imaging agents. The diamines are analogues of the previously reported selenium-75 labeled diamines, which show high brain uptake and retention. All of the radioiodinated amines display high initial brain uptake in rats after intravenous injection (1.7-2.4% dose/organ). The xylylenediamines show prolonged brain retention (t1/2 approximately 18 h), which is desirable for brain imaging. In contrast, the benzylamine is rapidly cleared from brain tissue (t1/2 approximately 15 min).