RESUMO
Two radiopharmaceuticals, technetium 99m-N-(2-mercapto-1-oxopropyl)glycine (99mTc-I) and technetium 99m-ethylenediamine-N,N'-bis(alpha-2-hydroxy-5-bromophenyl)acetic acid (99MTc-II), were prepared and evaluated in dogs, rabbits, and rats. Both agents gave good scintigraphic images of the liver and gallbladder in dogs. The cumulative amount of 99mTc-I and 99mTc-II excreted in the bile of dogs and the physiological disposition data in rats revealed slight, inconclusive differences in their distributions. However, the scintigraphic images and physiological disposition data in rabbits revealed gross differences in the distribution pattern of the two agents. The observed similarities in the biliary excretion of both agents in dogs and rats were attributed to the fact that these species are relatively good biliary excretors, and both agents therefore were excreted extensively. However, rabbits, which are poor biliary excretors relative to dogs and rats, excreted 99mTc-II more extensively than 99mTc-I because of the favorable molecular characteristics of 99mTc-II.