153Sm3+ and 111In3+ DTPA derivatives with high hepatic specificity: in vivo and in vitro studies

Abstract

Two DTPA derivatives, a mono-amide derivative containing an iodinated synthon, DTPA-IOPsp (L1) and the ligand DTPA(BOM)3 (BOM=benzyloxymethyl) (L2), radiolabelled with 153Sm3+ and 111In3+, were studied as potential hepatospecific gamma scintigraphic agents. In vivo studies with Wistar rats show that the main excretory pathway for all the chelates studied is the hepatobiliary system. The complexes of L2 show even greater hepatobiliary specificity than L1, perhaps as a consequence of longer blood circulation times due to their strong affinity towards HSA. The 153Sm3+ chelates are also more hepatospecific than the corresponding 111In3+ chelates. The La3+ and In3+ chelates of L1 and L2 show some structural and dynamic differences in aqueous solution, as studied by 1H NMR spectroscopy. While only two nona-coordinated isomers were observed for the La3+ complexes with both ligands, its number is much larger in the In3+ complexes, with both octa- and hepta-coordinated species (with unbound side arms), as well as structural isomers for each coordination number.