Metabolic disposition of cytembena in rats and dogs

1. The metabolic disposition of cytembena (sodium cis-3-p-methoxybenzoyl-3-bromoacrylate)labelled at both carbonyl carbon atoms was studied in rats and dogs. 2. Rats excreted over 70% and dogs excreted over 50% of the radioactive dose in 24 h. Most of the radioactivity was found in urine. Kidney retained the highest level of radioactivity after 24 h. Renal cortex was responsible for the observed high retention. Both species exhibited similar tissue distribution and urinary metabolic patterns. 3. Cytembena was metabolized by demethylation catalysed by microsomes and by debromination and double bond saturation catalysed by the 100,000 g supernatant fraction in the presence of glutathione and NADPH. Tentative structures of the metabolites identified by mass spectrometry and the probable metabolic pathway of cytembena are presented,