Formation of a novel free radical metabolite from CCl4 in the perfused rat liver and in vivo

Journal Article · Sat Apr 05 04:00:00 EST 1986 · J. Biol. Chem.; (United States)

OSTI ID:5736478

Connor, H D; Thurman, R G; Galizi, M D; Mason, R P

Electron spin resonance spectroscopy has been used to monitor free radicals formed during CCl4 metabolism by perfused livers from phenobarbital-treated rats. Livers were perfused simultaneously with the spin trap phenyl N-t-butylnitrone and with either 12CCl4 or 13CCl4. Perfusate samples and CHCl3:CH3OH extracts of perfusate and liver samples were analyzed for phenyl N-t-butylnitrone radical adducts of reactive free radicals. In the organic extracts, hyperfine coupling constants and 13C isotope effects observed in the ESR spectra indicated the presence of the radical adduct of the trichloromethyl radical. Surprisingly, an additional free radical signal about two orders of magnitude more intense than that of the phenyl N-t-butylnitrone/CCl.3 radical adduct was observed in the aqueous liver perfusate. This adduct was also detected by ESR in rat urine 2 h after intragastric addition of spin trap and CCl4. This radical adduct had hyperfine coupling constants and 13C isotope effects identical with the radical adduct of the carbon dioxide anion radical (CO2-.). Analysis of the pH dependence of the coupling constants yielded a pK alpha of 2.8 for the CO2-. radical adduct formed either in the perfused liver or chemically. Carbon tetrachloride is converted into CCl.3 by cytochrome P-450 through a reductive dehalogenation. The trichloromethyl free radical reacts with oxygen to form the trichloromethyl peroxyl radical, CCl3OO., which may be converted into .COCl and then trapped. This radical adduct would hydrolyze to the carboxylic acid form, which is detected spectroscopically. Alternatively, the carbon dioxide anion free radical could form through complete dechlorination and then react with the spin trap to give the CO2-. radical adduct directly.

• Research Organization: National Institute of Environmental Health Sciences, Research Triangle Park, NC
• OSTI ID: 5736478
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 10; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

560305* -- Chemicals Metabolism & Toxicology-- Vertebrates-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
BODY
CARBON 12
CARBON 13
CARBON ISOTOPES
CARBON TETRACHLORIDE
CHALCOGENIDES
CHLORINATED ALIPHATIC HYDROCARBONS
DIGESTIVE SYSTEM
ELECTRON SPIN RESONANCE
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GLANDS
HALOGENATED ALIPHATIC HYDROCARBONS
IN VITRO
ISOTOPES
LIGHT NUCLEI
LIVER
MAGNETIC RESONANCE
MAMMALS
METABOLISM
METABOLITES
NITROGEN COMPOUNDS
NITROGEN OXIDES
NUCLEI
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANS
OXIDES
OXYGEN COMPOUNDS
RADICALS
RATS
RESONANCE
RODENTS
STABLE ISOTOPES
VERTEBRATES