Toxicity of paracetamol in cultured chick hepatocytes treated with methotrexate

Lindenthal, John; Sinclair, Jacqueline F.; Howell, Scott K.; Cargill, Innes; Sinclair, Peter R.; Taylor, Thomas H.

doi:10.1016/0926-6917(93)90063-v

Cited by 5 publications

(3 citation statements)

References 34 publications

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“…Cell lysates were harvested using the Dual Luciferase kit and the lysates were analyzed on an Lmax microplate luminometer (Molecular Devices, Sunnyvale, CA). Protein synthesis, serving as an indicator of toxicity (Lindenthal et al, 1993;Kostrubsky et al, 1997a), was measured by the incorporation of [ 14 C]leucine (specific radioactivity, 0.1 mCi/mmol, 0.2 Ci/ plate) into protein for 1 h at the end of the overnight incubation with APAP, as previously described (Kostrubsky et al, 1997a).…”

Section: Methodsmentioning

confidence: 99%

“…Ten microliters of plasma were mixed with 20 l of extraction solution (2% perchloric acid with 0.1 mg/ml theophylline as an internal standard). APAP, APAP-Gluc, APAP-SO 4 , and APAP-SG in the resulting extract were separated and quantified by HPLC using the methods of Gemborys and Mudge (1981) and Lindenthal et al (1993) with the following modifications. The HPLC system consisted of a Milton Roy CM4000 Multiple Solvent Delivery System and SM4000 Programmable Wavelength Detector (Milton Roy Company, Rochester, NY), and a Thermo Separations Product Spectra System AS3000 autosampler with a 50-l loop (Thermo Electron Corporation, Waltham, MA).…”

Section: Methodsmentioning

confidence: 99%

“…Transportation of [ 3 H]vinblastine sulfate was included as the positive control. APAP was measured in the media by HPLC as described previously (Lindenthal et al, 1993).…”

Section: Methodsmentioning

confidence: 99%

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Role of the nuclear receptor PXR in acetaminophen hepatotoxicity

Wolf

Wood²,

Hunt³

et al. 2005

Drug Metabolism and Disposition

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ABSTRACT:The pregnane X receptor (PXR) is a transcriptional regulator of xenobiotic metabolizing enzymes, including cytochrome P450 3A (CYP3A), and transporters. Pretreatment of mice and rats with inducers of CYP3A increases acetaminophen (APAP) hepatotoxicity. In untreated mice, the amount of hepatic CYP3A11 mRNA is 4-fold greater in PXR(؊/؊) mice compared to wild-type mice (Guo et al., 2003), a finding anticipated to increase APAP hepatotoxicity in PXR(؊/؊) mice. We investigated APAP hepatotoxicity in wildtype and PXR(؊/؊) mice in a C57BL/6 background, with APAP administered by gavage. Despite a 2.5-fold higher level of total hepatic CYP3A protein and a 3.6-fold higher level of CYP3A activity compared to wild-type mice, PXR(؊/؊) mice were less sensitive to APAP hepatotoxicity. Hepatic levels of CYP2E1 were identical in the two mouse lines, but hepatic CYP1A2 levels were 3-fold greater in wild-type mice compared to PXR(؊/؊) mice. Caffeine, an inhibitor of CYP1A2 activity and an enhancer of CYP3A activity, decreased APAP hepatotoxicity in wild-type mice. APAP uptake was 1.5-fold greater in wild-type mice compared to PXR(؊/؊) mice. No significant differences in the formation of APAP glucuronide and sulfate-conjugated metabolites were observed between wild-type and PXR(؊/؊) mice. Glutathione levels were similar in the two mouse lines and were transiently decreased to similar amounts after APAP administration. Our finding that APAP hepatotoxicity was decreased in PXR(؊/؊) mice indicates that PXR is an important modulator of APAP hepatotoxicity, through positive modulation of constitutive CYP1A2 expression and possibly through increased APAP absorption.Acetaminophen (APAP) is an over-the-counter drug commonly used for its analgesic and antipyretic properties. It is also a component of numerous prescription medications. This compound is considered relatively safe at therapeutic doses; however, when taken in overdose, it has been shown to produce potentially fatal centrilobular hepatic necrosis (for review, see James et al., 2003).At pharmacological doses, APAP is mainly metabolized by phase II xenobiotic-metabolizing enzymes via sulfation and glucuronidation. A small amount of APAP is converted to N-acetyl-p-benzoquinone imine (NAPQI), a reactive metabolite, via cytochromes P450 (P450s) (for review, see James et al., 2003). NAPQI is detoxified by conjugation with glutathione (GSH); however, in APAP overdose, the capacities of phase II pathways are overwhelmed and GSH levels become depleted (for review, see James et al., 2003). The ensuing liver damage may be due to the binding of NAPQI to proteins, the generation of reactive oxygen species, or a combination of both (for review, see James et al

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%