Acetaminophen toxicity in fed and fasted mice

1982 ◽  
Vol 60 (3) ◽  
pp. 399-404 ◽  
Author(s):  
Robin M. Walker ◽  
Thomas E. Massey ◽  
Timothy F. McElligott ◽  
William J. Racz
Keyword(s):  
Covalent Binding ◽  
Microsomal Protein ◽  
Transferase Activity ◽  
Reactive Metabolite ◽  
Metabolite Formation ◽  
Acetaminophen Toxicity ◽  
Aryl Hydrocarbon ◽  
Significant Difference ◽  
Aryl Hydrocarbon Hydroxylase Activity ◽  
Liver Enlargement

Acetaminophen (750 mg/kg) toxicity and its modification by N-acetylcysteine (NAC, 1200 mg/kg) have been compared in fed and fasted mice. There was no significant difference between fed and fasted animals with respect to microsomal protein content, cytochrome(s) P-450 content, and aryl hydrocarbon hydroxylase activity. Glucuronyl transferase activity was significantly higher in fasted mice. Hepatotoxicity, as determined histologically and by liver enlargement was greater in fasted than fed mice. Covalent binding of [3H]acetaminophen metabolite(s) to liver proteins was also greater in fasted animals. NAC administration prevented acetaminophen-induced microscopic changes and liver enlargement and reduced the magnitude of covalent binding of acetaminophen metabolites. Fasting caused a marked fall in liver reduced sulfhydryl concentration. The incidence of acetaminophen-induced hypothermia was greater in fasted than in fed animals. NAC administration reduced hypothermia in fasted mice and abolished it in fed animals. It is concluded that enhanced acetaminophen toxicity in fasted mice compared with fed mice is unlikely to be a consequence of increased reactive metabolite formation, but rather a result of reduced inactivation of reactive metabolite(s) due to reduced hepatic glutathione stores in fasted mice.

Pulmonary toxicity of 1,1-dichloroethylene: correlation of early changes with covalent binding

1986 ◽  
Vol 64 (2) ◽  
pp. 112-121 ◽  
Author(s):  
P. G. Forkert ◽  
V. Stringer ◽  
K. M. Troughton
Keyword(s):  
Structural Damage ◽  
Covalent Binding ◽  
Significant Inhibition ◽  
Clara Cells ◽  
Aryl Hydrocarbon Hydroxylase ◽  
Hydroxylase Activity ◽  
Aryl Hydrocarbon ◽  
Temporal Correlations ◽  
Aryl Hydrocarbon Hydroxylase Activity ◽  
Cytochrome P 450

Administration of a single intraperitoneal dose of 1,1-dichloroethylene (125 mg/kg,1,1-DCE) to mice resulted in bronchiolar injury with selective necrosis of Clara cells. Degenerative changes were manifest in Clara cells as early as 1 h following 1,1-DCE exposure, and were characterized by marked swelling of mitochondria and aggregation of chromatin against the nuclear membrane. Cell death was apparent at 2 h; by 8 h, areas of the bronchiolar epithelium were devoid of lining cells, and at 24 h, the majority of Clara cells were exfoliated. The residual epithelium consisted of flattened cells which formed a thin lining for the airway. Necrosis of Clara cells early in the course of 1,1-DCE exposure coincided with peak covalent binding of [14C] 1,1-DCE and significant depression of components of the pulmonary mixed-function oxidase system; cytochrome P-450 and aryl hydrocarbon hydroxylase activity were markedly reduced but not depleted. Liver damage involving centrilobular hepatocytes was observed at 24 h in 30% of treated animals, and coincided with significant inhibition of aryl hydrocarbon hydroxylase activity; cytochrome P-450 content, however, remained unchanged. While changes in the liver evoked by 1,1-DCE were less striking, the results in lung demonstrate positive temporal correlations between structural damage, peak covalent binding and disturbances of monooxygenase enzymes.

Role of Phase II Enzymes in the Bioactivation of 1,4-Dichlorobenzene and 1,4-Dibromobenzene

1996 ◽  
Vol 24 (4) ◽  
pp. 603-608
Author(s):  
Moreno Paolini ◽  
Laura Pozzetti ◽  
Renata Mesirca ◽  
Andrea Sapone ◽  
Paola Silingardi ◽  
...  
Keyword(s):  
Dna Binding ◽  
Phase I ◽  
Phase Ii ◽  
Covalent Binding ◽  
Fold Increase ◽  
Test System ◽  
Oxidative Enzymes ◽  
Transferase Activity ◽  
Genetic Toxicology

The use of sodium phenobarbital (PB, CYP2B1 inducer) combined with β-naphthoflavone (β-NF, 1A1) to induce certain Phase I reactions in S9 liver fractions is a standard method for conducting short-term bioassays for genotoxicity. However, because post-oxidative enzymes are also able to activate many precarcinogens, we tested the possibility of adapting S9 liver fractions derived from Phase II-induced rodents to the field of genetic toxicology. In this study, S9 liver fractions derived from Swiss albino CD1 mice fed 7.5g/kg 2-(3)-tert-butyl-4-hydroxyanisole (BHA; a monofunctional Phase II-inducer) for 3 weeks, show a clear pattern of induction with an approximately 3.5–9.5-fold increase in glutathione S-transferase activity. In vitro DNA binding of the promutagenic agents, [14C]-l,4-dichlorobenzene (DCB) and [14C]-1,4-dibromobenzene (DBB), is mediated by such metabolic liver preparations and showed a significant increase in covalent binding capability. In some instances, enzyme activity was more elevated when compared to that obtained with traditional (Phase I-induced) S9. Together with DNA binding, the genetic response of these chemicals in the diploid D7 strain of Saccharomyces cerevisiae used as a biological test system, revealed the ability of the BHA-derived preparations to activate the promutagenic agents, as exemplified by the significant enhancement of mitotic gene-conversion (up to 5.2-fold for DCB and 3.4-fold for DBB) and reverse point mutation (up to 3.6-fold for DCB and 2.5-fold for DBB) at a 4mM concentration. This novel metabolising biosystem, with enhanced Phase II activity, is recommended together with a traditional S9, for detecting unknown promutagens in genotoxicity studies. The routine use of either oxidative or post-oxidative S9 increases the responsiveness of the test and can contribute to the identification of promutagens not detected when using traditional protocols.

scholarly journals Identification of a functionally conserved surface region of rat cytochromes P450IA

1991 ◽  
Vol 278 (3) ◽  
pp. 749-757 ◽  
Author(s):  
R J Edwards ◽  
A M Singleton ◽  
B P Murray ◽  
S Murray ◽  
A R Boobis ◽  
...  
Keyword(s):  
Affinity Purification ◽  
Cytochromes P450 ◽  
Surface Region ◽  
Carrier Protein ◽  
Peptide Antigen ◽  
Aryl Hydrocarbon ◽  
C Terminus ◽  
Aryl Hydrocarbon Hydroxylase Activity ◽  
The Difference ◽  
Peptide Antibodies

A region of rat cytochrome P450IA1 at residues 294-301 (Gln-Asp-Arg-Arg-Leu-Asp-Glu-Asn), equivalent to a proinhibitory region of cytochrome P450IA2, was identified by sequence alignment. Anti-peptide antibodies were successfully raised when the peptide was coupled through either its N- or its C-terminus to carrier protein, but no antibodies were produced against the so-called multiple peptide antigen, which consisted of eight copies of the peptide attached through its C-terminus to a synthetic base. Both of the anti-peptide antibodies bound specifically to cytochrome P450IA1 in the rat, as shown by e.l.i.s.a. and immunoblotting. They inhibited microsomal aryl hydrocarbon hydroxylase activity and the mutagenic activation of 2-acetylaminofluorene (these reactions are catalysed by cytochrome P450IA1), but not high-affinity phenacetin O-de-ethylation activity, which is catalysed by cytochrome P450IA2. However, there was differences in the properties of the two antisera in their binding to cytochromes P450IA1 in species other than the rat, their relative binding to the multiple peptide antigen, the yield of antibody following affinity purification using peptide coupled through its N-terminus to CNBr-activated Sepharose, and the binding of the purified preparations to N- and C-terminal-coupled peptide conjugates. These observations indicated that the antibodies were directed to the region of the peptide opposite to the end which was coupled to the carrier protein. Nevertheless, both of the antibody preparations bound equally well to the target cytochrome P450, thus indicating that, in the native protein, the whole of the peptide region is exposed on the surface of cytochrome P450IA1 and is available for binding by the antibodies. The role of this region appears to be the same in both cytochromes P450IA1 and P450IA2, despite the difference in its primary structure in the two cytochromes P450.

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