Back to Search Start Over

Inhibition of Carbamyl Phosphate Synthetase-I and Glutamine Synthetase by Hepatotoxic Doses of Acetaminophen in Mice

Authors :
Sanjiv Gupta
Lynette K. Rogers
Sarah K. Taylor
Charles V. Smith
Source :
Toxicology and Applied Pharmacology. 146:317-327
Publication Year :
1997
Publisher :
Elsevier BV, 1997.

Abstract

The primary mechanisms proposed for acetaminophen-induced hepatic necrosis should deplete protein thiols, either by covalent binding and thioether formation or by oxidative reactions such as S-thiolations. However, in previous studies we did not detect significant losses of protein thiol contents in response to administration of hepatotoxic doses of acetaminophen in vivo. In the present study we employed derivatization with the thiol-specific agent monobromobimane and separation of proteins by SDS–PAGE to investigate the possible loss of specific protein thiols during the course of acetaminophen-induced hepatic necrosis. Fasted adult male mice were given acetaminophen, and protein thiol status was examined subsequently in subcellular fractions isolated by differential centrifugation. No decreases in protein thiol contents were indicated, with the exception of a marked decrease in the fluorescent intensity, but not of protein content, as indicated by staining with Coomassie blue, of a single band of approximately 130 kDa in the mitochondrial fractions of acetaminophen-treated mice. This protein was identified by isolation and N-terminal sequence analysis as carbamyl phosphate synthetase-I (CPS-I) (EC 6.3.4.16). Hepatic CPS-I activities were decreased in mice given hepatotoxic doses of acetaminophen. In addition, hepatic glutamine synthetase activities were lower, and plasma ammonia levels were elevated in mice given hepatotoxic doses of acetaminophen. The observed hyperammonemia may contribute to the adverse effects of toxic doses of acetaminophen, and elucidation of the specific mechanisms responsible for the hyperammonemia may prove to be useful clinically. However, the preferential depletion of protein thiol content of a mitochondrial protein by chemically reactive metabolites generated in the endoplasmic reticulum presents a challenging and potentially informative mechanistic question.

Details

ISSN :
0041008X
Volume :
146
Database :
OpenAIRE
Journal :
Toxicology and Applied Pharmacology
Accession number :
edsair.doi.dedup.....a7a595c053e8e3148d634df6bbe4c9fc
Full Text :
https://doi.org/10.1006/taap.1997.8228