Cytotoxicity and metabolism of the hepatotoxin N-methylformamide and related formamides in mouse hepatocytes.
Some N-alkylformamides such as N-methylformamide (NMF) possess hepatotoxic properties in vivo. To study the mechanism of this toxicity, suspensions of mouse hepatocytes were tested as an in vitro model system suitable for the study of the relationship between (i) the toxic potential of formamides, (ii) their metabolism to N-alkylcarbamoylating species, and (iii) their ability to deplete hepatic glutathione pools. The effects of NMF were compared with those of its analogs N-ethylformamide (NEF), N,N-dimethylformamide (DMF), formamide (F), N-methylacetamide (NMA), and N-methyldeuteroformamide ([2H]NMF). Only NEF and [2H]NMF share with NMF the ability to cause liver damage in vivo in mice. Hepatocellular toxicity was determined by measuring LDH leakage into the extracellular medium; metabolism to N-alkylcarbamoylating species was measured by GLC after derivatization with propanol to form propyl N-alkylcarbamate; glutathione concentrations were determined spectrophotometrically. Of the formamide analogs studied, only NMF and NEF caused cytotoxicity, being apparently equipotent. NMF, NEF, and [2H]NMF gave rise to the formation of detectable levels of N-alkylcarbamoylating metabolites and depleted glutathione pools. Toxicity, metabolism, and glutathione depletion were dependent on NMF concentration. [2H]NMF was markedly less cytotoxic than NMF, yielding only 35% of the amount of N-methylcarbamoylating metabolite compared to NMF and caused less depletion of glutathione than did NMF. These results parallel closely the in vivo hepatotoxic potential of NMF and its analogs, their metabolism to urinary S-(N-alkylcarbamoyl)mercapturates and their ability to deplete hepatic glutathione in mice. The results provide support for the contention that metabolism is involved with formamide-induced hepatotoxicity and suggest that suspensions of isolated mouse hepatocytes are an appropriate in vitro model for the further study of the mechanism by which formamides cause toxicity.
Shaw
A J
AJ
Pharmaceutical Sciences Institute, Aston University, Birmingham, United Kingdom.
Gescher
A
A
Mráz
J
J
D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000633:toxicity*; D002219:Carbamates / Q000378:metabolism; D056486:Chemical and Drug Induced Liver Injury; D005559:Formamides / Q000378:metabolism / Q000633:toxicity*; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008107:Liver Diseases / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D013329:Structure-Activity Relationship
D000970:Antineoplastic Agents; D002219:Carbamates; D005559:Formamides; C052469:N-acetyl-S-(N-methylcarbamoyl)cysteine; C053323:S-(N-methylcarbamoyl)glutathione; C020401:N-methylcarbamate; D007770:L-Lactate Dehydrogenase; D005978:Glutathione; D000111:Acetylcysteine; C002950:methylformamide