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 (L 1 ) and the ligand DTPA(BOM) 3 (BOM=benzyloxymethyl) (L 2 ), radiolabelled with 153 Sm 3+ and 111 In 3+ , 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 L 2 show even greater hepatobiliary specificity than L 1 , perhaps as a consequence of longer blood circulation times due to their strong affinity towards HSA. The 153 Sm 3+ chelates are also more hepatospecific than the corresponding 111 In 3+ chelates. The La 3+ and In 3+ chelates of L 1 and L 2 show some structural and dynamic differences in aqueous solution, as studied by 1 H NMR spectroscopy. While only two nona-coordinated isomers were observed for the La 3+ complexes with both ligands, its number is much larger in the In 3+ complexes, with both octa- and hepta-coordinated species (with unbound side arms), as well as structural isomers for each coordination number.