Abstract
1. The published work on the behaviour of trichlorofluoromethane in biological systems is discussed and compared with carbon tetrachloride and halothane. 2. The possible metabolism of trichlorofluoromethane by liver microsomal preparations in vitro under aerobic and anaerobic conditions has been investigated. Evidence is presented which suggests that metabolism occurs under both of these conditions. The rate of oxidative metabolism was found to be similar to that of carbon tetrachloride. In anaerobic microsomal preparations fortified with NADPH trichlorofluoromethane exhibited a Soret maximum at 452 nm in the difference spectrum. 3. Experiments in which [[14]C] trichlorofluoromethane was dosed orally to rats support the findings in vitro and show the formation of metabolites in the expired air and urine. The major metabolite was carbon dioxide. 4. [14]C-labelled metabolites of trichlorofluoromethane were found to bind irreversibly to liver microsomal proteins and lipids in vitro. The possibility of similar reactions occurring in vivo is discussed. 5. Evidence is presented which indicates the involvement of the hepatic microsomal mixed function oxidase system in the metabolism of trichlorofluoromethane. In this respect trichlorofluoromethane is very similar to carbon tetrachloride but is not hepatotoxic. This phenomenon is discussed in relation to the possible mechanisms of halogenated hydrocarbon hepatotoxicity.