The key role of cytochromes P-450 in the metabolism and toxicity of volatile anesthetic agents and the ready inducibility of these enzymes provides for potentially hazardous drug-anesthetic interactions. The overall aims of this investigation are to determine microsomal metabolism of volatile, halogenated anesthetics and the contribution of this metabolism to the potential toxicity of the anesthetic agents under the influence of inducing xenobiotics. We propose to complete studies of the toxicity and metabolism of the anesthetic fluroxene and to initiate studies of the recently introduced anesthetics isoflurane and sevoflurane and their metabolites, 2,2,2-trifluoroethanol (TFE), trifluoroacetaldehyde, and trifluoroacetic acid. Metabolic pathways will be determined by combining data from in vitro microsomal systems, isolated hepatocyte cultures, reconstituted cytochrome P-450 systems, and in vivo experiments. Additional specific aims are: to determine the molecular mechanism of TFE-induced bone marrow depression using in vivo and in vitro determinations of the effects of TFE and TFE metabolites on protein synthesis, DNA synthesis, RNA synthesis, and covalent binding of reactive metabolites to cellular macromolecules; to determine the mechanisms of synergistic toxic interactions of endotoxin and TFE, and of endotoxin and isoflurane and to compare them to that of halothane and endotoxin, which also leads to increased toxicity; and to determine the reason for the observed sex differences in sensitivity to the toxicity of anesthetics and metabolites. The effect of sex specific steroids on cytochrome P-450 metabolism of anesthetics and metabolites will be determined. Toxicity will be assessed by observations of lethality, serum glutamate-pyruvate transaminase activity, blood urea nitrogen, serum cholinesterase, white blood cell count, and histopathology. The role of specific cytochrome P-450 isozymes will be assessed with the use of a variety of inducing agents including ethanol, phenobarbital, and beta-naphthoflavone. An understanding of the influence of inducing agents of cytochrome P-450 on anesthetic metabolism/toxicity, particularly on tissue growth and the hemopoietic system, will provide the basis for evaluating drug-anesthetic interactions for which there is such a rich potential in the surgical environment, where infection control and tissue growth are very important. The data will also provide insight into the potential toxic interactions of the anesthetics with concomitant bacterial infections.
