The Metabolism and Toxicity of Furosemide in the Wistar Rat and Cd-1 Mouse: a Chemical and Biochemical Definition of the Toxicophore.
From: Drug Safety Research Group, Department of Pharmacology and Therapeutics, University of Liverpool, Sherrington Buildings, Ashton Street, Liverpool, Merseyside L69 3GE, UK. dom@liv.ac.uk
The Journal of pharmacology and experimental therapeutics
- Publish Date: Sep 2007
- ISSN: 0022-3565
- Volume: 322
- Issue: 3
- Pages: 1208-20
- Medium: Print
- Language: English
- Citation (JAMA): Williams Dominic P, Antoine Daniel J, Butler Philip J, et al. The Metabolism and Toxicity of Furosemide in the Wistar Rat and Cd-1 Mouse: a Chemical and Biochemical Definition of the Toxicophore.. J. Pharmacol. Exp. Ther. Sep 2007;322:1208-20
Abstract
Furosemide, a loop diuretic, causes hepatic necrosis in mice. Previous evidence suggested hepatotoxicity arises from metabolic bioactivation to a chemically reactive metabolite that binds to hepatic proteins. To define the nature of the toxic metabolite, we examined the relationship between furosemide metabolism in CD-1 mice and Wistar rats. Furosemide (1.21 mmol/kg) was shown to cause toxicity in mice, but not rats, at 24 h, without resulting in glutathione depletion. In vivo covalent binding to hepatic protein was 6-fold higher in the mouse (1.57 +/- 0.98 nmol equivalent bound/mg protein) than rat (0.26 +/- 0.13 nmol equivalent bound/mg protein). In vivo covalent binding to mouse hepatic protein was reduced 14-fold by a predose of the cytochrome P450 (P450) inhibitor, 1-aminobenzotriazole (ABT; 0.11 +/- 0.04 nmol equivalent bound/mg protein), which also reduced hepatotoxicity. Administration of [(14)C]furosemide to bile duct-cannulated rats demonstrated turnover to glutathione conjugate (8.8 +/- 2.8%), gamma-ketocarboxylic acid metabolite (22.1 +/- 3.3%), N-dealkylated metabolite (21.1 +/- 2.9%), and furosemide glucuronide (12.8 +/- 1.8%). Furosemide-glutathione conjugate was not observed in bile from mice dosed with [(14)C]furosemide. The novel gamma-ketocarboxylic acid, identified by nuclear magnetic resonance spectroscopy, indicates bioactivation of the furan ring. Formation of gamma-ketocarboxylic acid was P450-dependent. In mouse liver microsomes, a gamma-ketoenal furosemide metabolite was trapped, forming an N-acetylcysteine/N-acetyl lysine furosemide adduct. Furosemide (1 mM, 6 h) became irreversibly bound to primary mouse and rat hepatocytes, 0.73 +/- 0.1 and 2.44 +/- 0.3 nmol equivalent bound/mg protein, respectively, which was significantly reduced in the presence of ABT, 0.11 +/- 0.03 and 0.21 +/- 0.1 nmol equivalent bound/mg protein, respectively. Furan rings are part of new chemical entities, and mechanisms underlying species differences in toxicity are important to understand to decrease the drug attrition rate.
Mesh Headings (Keywords): Animals, Cells, Cultured, Cytochrome P-450 Enzyme System, Furosemide, Glutathione, Hepatocytes, Mice, Microsomes, Liver, Protein Binding, Rats, Rats, Wistar, Species Specificity
Check for Full Text / PubMed Unique Identifier (PMID): 17556636
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