Potential tumor- or organ-imaging agents. 26. Polyiodinated 2-substituted triacylglycerols as hepatographic agents.

A series of omega-(3-amino-2,4,6-triiodophenyl)alkanoic acids and the corresponding 1,3-dipalmitoylglycerol 2-[omega-(3-amino-2,4,6-triiodophenyl)alkanoates] were synthesized, radioiodinated with iodine-125, and evaluated for their ability to selectively localize in the liver for potential use as hepatographic imaging agents. Acid analogues 1d and 1e afforded relatively high levels of radioactivity in the liver (45 and 49% injected dose) 5 min after intravenous administration to rats. These acids displayed a marked propensity to become bound to plasma albumin. In contrast, triacylglycerol analogues 10a and 10c did not become immediately associated with plasma albumin but instead rapidly became associated with plasma lipoproteins and showed a different tissue distribution profile than free acids 1a and 1c. Although long-chain triacylglycerol analogues 10d and 10e exhibited some capacity to accumulate in the liver at 5 and 30 min, respectively, analysis of the plasma revealed significant in vivo ester hydrolysis. It would thus appear that liver radioactivity following administration of 10d and 10e was due to uptake of the free acid and not the intact triacylglycerol. Triacylglycerol analogues 10a and 10c, on the other hand, were taken up intact and showed liver accumulations of 25 and 35% of the administered dose at 30 min.