Evaluation of sup(99m)Tc-HIDA complex as a cholescintigraphic agent

In the reaction labeling N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid (HIDA) with sup(99m)Tc, several complexes with different chemical characteristics were observed to occur with slight changes in the labeling conditions. Among these complexes, a complex detected in the bile of rats was limited to one complex, named as complex II. The preparation method of sup(99m)Tc-HIDA complex II and the exchange reaction between this complex and penicillarmine indicate that sup(99m)Tc is coordinated with HIDA as low-hydrolyzed sup(99m)Tc in this complex. This complex is excreted rapidly through the bile and, within 1 hr, about 65% of the total activity injected is recovered from bile in rats. The organ distribution of this complex was studied in mice by radioassay and in rabbits by scintillation camera and, in both cases, the radioactivity was accumulated in the gallbladder. These results suggest that the sup(99m)Tc chemical state, low-hydrolyzed state, relates to the bile excretion behavior of this complex, a potentially useful cholescintigraphic agent. (auth.)