Effects of brotizolam on mixed-function oxidases and glutathione metabolism in the rat

Abstract

1. Intra-gastric administration of brotizolam (0.1–200 mg/kg) daily for three days to rats resulted in no significant changes in the hepatic and intestinal cytochrome P-450-dependent or P-448-dependent mixed-function oxidases, or in the hepatic flavoprotein dimethylaniline N-oxidase.

2. Liver microsomes from mouse, rat and man metabolized brotizolam by hydroxylation of the diazepine ring and of the methyl group at rates which were greater for mouse > rat > man. Brotizolam and its metabolites generated by rat-liver microsomes in vitro were not mutagenic in the Ames' test.

3. Brotizolam, at 200 mg/kg per day for two to six weeks, depleted liver glutathione concentration and markedly increased liver γ-glutamyl transpeptidase, glutathione reductase and glutathione transferase activities. Similar changes were not seen at the lower dose of 0.3 mg/kg.

4. The observed increases in glutathione metabolism and the decreased tissue concentration of glutathione are indicative of high levels of glutathione conjugation, and provide a possible explanation for the equivocal increase in tumorigenicity seen in rats receiving brotizolam at high dosage.