Bioactivation and cytotoxicity of 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) in isolated rat hepatocytes.
The bioactivation and cytotoxicity of 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), a replacement for some ozone-depleting chlorofluorocarbons, were investigated using freshly isolated hepatocytes from non-induced male rats. A time- and concentration-dependent increase in the leakage of lactate dehydrogenase and a concentration-dependent loss of total cellular glutathione were observed in cells incubated with 1, 5 and 10 mM HCFC-123 under normoxic or hypoxic (about 4% O2) conditions. Lactate dehydrogenase leakage was completely prevented by pretreating the cell suspension with the free radical trapper N-t-butyl-alpha-phenylnitrone. The aspecific cytochrome P450 (P450) inhibitor, metyrapone, totally prevented the lactate dehydrogenase leakage from hepatocytes, while two isoform-specific P450 inhibitors, 4-methylpyrazole and troleandomycin (a P450 2E1 and a P450 3A inhibitor, respectively), provided a partial protection against HCFC-123 cytotoxicity. Interestingly, pretreatment of cells with glutathione depletors, such as phorone and diethylmaleate, did not enhance the HCFC-123-dependent lactate dehydrogenase leakage. Two stable metabolites of HCFC-123, 1-chloro-2,2,2-trifluoroethane and 1-chloro-2,2-difluoroethene, were detected by gas chromatography/mass spectrometry analysis of the head space of the hepatocyte incubations carried out under hypoxic and, although at a lower level, also normoxic conditions, indicating that reductive metabolism of HCFC-123 by hepatocytes had occurred. The results overall indicate that HCFC-123 is cytotoxic to rat hepatocytes under both normoxic and hypoxic conditions, due to its bioactivation to reactive metabolites, probably free radicals, and that P450 2E1 and, to a lower extent, P450 3A, are involved in the process.
Ferrara
R
R
Dept. of Environmental Medicine and Public Health, University of Padova, Italy.
Zanovello
A
A
Bortolato
S
S
White
I N
IN
Manno
M
M
D000818:Animals; D017402:Chlorofluorocarbons / Q000378:metabolism*; D064227:Chlorofluorocarbons, Ethane; D003497:Cyclic N-Oxides; D004305:Dose-Response Relationship, Drug; D000077604:Fomepizole; D008401:Gas Chromatography-Mass Spectrometry; D005978:Glutathione / Q000378:metabolism; D006221:Halothane / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D066298:In Vitro Techniques; D007659:Ketones / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D008298:Maleates / Q000494:pharmacology; D009589:Nitrogen Oxides / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014217:Troleandomycin / Q000494:pharmacology
D017402:Chlorofluorocarbons; D064227:Chlorofluorocarbons, Ethane; D003497:Cyclic N-Oxides; D007659:Ketones; D008298:Maleates; D009589:Nitrogen Oxides; D011720:Pyrazoles; D011725:Pyridines; C013109:metapyrone; C067411:2,2-dichloro-1,1,1-trifluoroethane; C029217:phenyl-N-tert-butylnitrone; C016800:1,1,1-trifluoro-2-chloroethane; D000077604:Fomepizole; C018637:phorone; D014217:Troleandomycin; D007770:L-Lactate Dehydrogenase; C014476:diethyl maleate; D005978:Glutathione; D006221:Halothane