Influences of glutathione status on different cytocidal responses of monolayer rat hepatocytes exposed to aflatoxin B1 or acetaminophen.
In short-term primary monolayer cultures of rat hepatocytes, aflatoxin B1 (AFB1) causes a characteristic prelethal cytomorphological response in which peripheral attached cytoplasm contracts segmentally to form finger-like blebs. This response precedes lethal injury as detected by release of lactate dehydrogenase (LDH) into culture medium. We compared the influences of various modifiers of cellular glutathione (GSH) status on cytocidal responses of Fischer 344 rats hepatocytes exposed to AFB1 or acetaminophen (AAP), a hepatotoxin which does not produce segmental cytoplasmic contraction. N-Acetylcysteine (4 mM) reduced the degree of LDH release by AAP (4 to 16 mM) but was not protective against cell killing by AFB1, although it slightly reduced the percentage of hepatocytes with segmental cytoplasmic contraction at 6 hr. BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) at 40 microM markedly inhibited glutathione reductase and also strongly potentiated cell killing by AAP but did not significantly influence segmental cytoplasmic contraction or LDH release in response to AFB1. Diethylmaleate (40 to 160 microM), a depletor of hepatocellular GSH, and buthionine-D,L-sulfoximine (4 mM), an inhibitor of GSH synthesis, each did not alter hepatocyte killing by AFB1 but were strong potentiators of toxicity of AAP. AAP inhibited glutathione reductase but AFB1 did not. Total GSH concentrations at 6 and 18 hr were reduced by AAP and to a lesser extent by AFB1 in comparison with control cultures. These findings demonstrate that, in contrast to AAP toxicity, the characteristic mode of hepatocyte killing by AFB1 in monolayer cultures is substantially independent of induced alterations in GSH. These results indicate that GSH-dependent detoxification mechanisms do not play a major role in removing necrogenic metabolites of AFB1 in Fischer 344 rat hepatocytes. They further suggest that prelethal responses of AFB1-injured hepatocytes are not affected by GSH-dependent cytoprotective mechanisms.
D000082:Acetaminophen / Q000633:toxicity*; D000111:Acetylcysteine / Q000494:pharmacology; D016604:Aflatoxin B1; D000348:Aflatoxins / Q000633:toxicity*; D000818:Animals; D002330:Carmustine / Q000494:pharmacology; D002478:Cells, Cultured; D004347:Drug Interactions; D005978:Glutathione / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344
D000348:Aflatoxins; D000082:Acetaminophen; D016604:Aflatoxin B1; D007770:L-Lactate Dehydrogenase; D005978:Glutathione; D002330:Carmustine; D000111:Acetylcysteine