HEPATOBILIARY AND RENAL EXCRETION IN MICE OF CHARGED AND NEUTRAL GADOLINIUM COMPLEXES OF CYCLIC TETRA-AZA-PHOSPHINIC AND CARBOXYLIC-ACIDS

Tissue distribution of 21 new Gd-157/153 complexes was measured at 5 m in and 24 hr after an intravenous injection into mice. A complex was j udged to be stable in vivo when the percentage of Gd-153 retained in t he liver and skeleton at 24 hr was comparable with that of Gd-153(DOTA )-. Complexes varied in net charge and lipophilicity and 20 were phosp hinic or carboxylic acid derivatives of tetra-aza-cyclo-dodecane. Thre e anionic, lipophilic complexes were cleared predominantly by the hepa to-biliary pathway and were stable in vivo. The remaining 18 complexes were cleared mainly by the kidneys. Of these 18, 1 anionic, 8 neutral , and 3 cationic complexes were stable in vivo. These findings augur w ell for the future of hepato-biliary and general purpose Gd contrast e nhancing agents for MRI.