A comparative study on the irreversible binding of labeled halothane trichlorofluoromethane, chloroform, and carbon tetrachloride to hepatic protein and lipids in vitro and in vivo

Abstract

1) After intraperitoneal injection of labeled CCl4, CHCl3, and halothane in mice, 14C is preferentially bound to liver endoplasmic protein and lipid. A considerable activity is also associated with mitochondrial constituents. Maximal protein binding (nmol/mg): CCl4: 2.8 (0.5 hrs); CHCl3: 11.5 (6 hrs); halothane: 5 (6 hrs). Lipid binding: CCl4: 6.4 (5 min); CHCl3: 8 (4 hrs); halothane: 13.5 (2 hrs). The form of the binding curves in microsomal and mitochondrial protein and lipid differed with the individual haloalkanes. 2) The irreversible (covalent) binding of 14C from labeled haloalkanes in anaerobic suspensions of isolated rabbit liver microsomes and NADPH after 30 min was for protein (lipid) (nmol/mg): CCl4: 15 (58); CHCl3: 3.4 (3.2); halothane: 2.3 (10); trichlorofluoromethane: 6.5 (30). Anerobic incubation favored dehalogenation, but CHCl3 metabolism and irreversible binding requires oxygen. The greatest differences in the in vitro "covalent" binding rates were observed with CHCl3 in rat, mouse, and rabbit. 3) Altered microsomal cytochrome P-450 concentrations in newborn animals, or produced by pretreatment of rats with phenobarbital, 3-methylcholanthrene (MC), or CoCl2 effected similar, but not proportional changes in the rates of irreversible protein and lipid binding. Upon addition of CCl4 the difference of light absorption of reduced liver microsomes from MC-pretreated rats containing cytochrome P-448 appeared at 452 nm. The irreversible binding rate in these microsomes was also increased. The small accleration in irreversible binding in liver microsomes from rats pretreated with isopropanol is not proportional to the high increase of CCl4 toxicity. 4) Practically no binding to added, soluble albumin or RNA was observed in microsomal incubates. However, 14C is bound to the nicotine-adenine dinucleotides of the NADPH system. All haloalkanes produced a similar increase of NADPH oxidation in incubates of rabbit liver microsomes and NADPH.

A review of the mutagenicity of chloroform

“…Therefore, the toxicity and carcinogenicity of CHC13 may be related to its metabolism to phosgene. Several studies demonstrate that reactive CHC13 metabolites covalently bind to protein and lipid [Sipes et al, 1977;Docks and Krishna, 1976;Uehleke and Werner, 1975;Uehleke et al, 1977;Ilett et al, 19731.…”

Dichloromethane Potentiation of Carbon Tetrachloride Hepatotoxicity in Rats

“…Microsomal protein content was determined by the method chloromethyl radicals can form covalent adducts with lipids of Lowry et al (1951). and proteins (Uehleke and Werner, 1975), interact with oxy-Microsomal conjugated diene concentrations were measured 1 hr postgen to form a trichloromethyl peroxy radical, or abstract treatment by the method of Klaassen and Plaa (1969) to evaluate lipid hydrogen atoms to form chloroform (Pohl et al, 1983). , 1966).…”

Characterization of a Phospholipid Adduct Formed in Sprague Dawley Rats by Chloroform Metabolism: NMR Studies

“…The binding of chloroform metabolites to microsomal and mitochondrial PLs has been demonstrated in mice (28). The binding of phosgene, the CHCl 3 oxidative metabolite, to the PL polar heads has also been shown in isolated microsomes and hepatocyte incubations and in vivo (6,7,29).…”