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Mutagenic activity of biliary metabolites of 6-hydroxymethylbenzo[a]pyrene
Abstract:
The biliary excretion of the carcinogen 6-hydroxy-methylbenzo[a]pyrene was investigated in rats after i.p. administration. Mutagenicity of the parent compound and its biliary metabolites was tested in Ames Salmonella/microsome mutagenicity assay. Approximately 40% of the dose administered (0.25-0.5 mg/kg) to the rats was excreted in the bile within 6 h. 6-Hydroxymethylbenzo[a]pyrene was excreted primarily as water-soluble metabolites, including glucuronide and sulfate conjugates. Negligible quantities of unchanged 6-hydroxymethylbenzo[a]pyrene were excreted in the bile. In the presence of Aroclor-induced S9, 6-hydroxymethylbenzo[a]pyrene was a potent mutagen. The mutagenicity of bile from rats treated with 6-hydroxymethylbenzo[a]pyrene was variable in the absence of an activation system. However, the same bile samples were mutagenic in the presence of beta-glucuronidase and/or S9. These results indicate that biliary metabolites of 6-hydroxymethylbenzo[a]pyrene can be metabolically activated to mutagenic species.
Insights
Biliary excretion of the carcinogen 6-hydroxymethylbenzo[a]pyrene in rats revealed significant metabolism. Bile contained conjugates, and metabolites were mutagenic upon activation, indicating potential health risks.
Area of Science:
- Environmental Health
- Toxicology
- Carcinogenesis
Background:
- 6-hydroxymethylbenzo[a]pyrene is a carcinogen requiring investigation into its metabolic fate.
- Biliary excretion is a key route for eliminating xenobiotics and their metabolites.
Purpose of the Study:
- To investigate the biliary excretion of 6-hydroxymethylbenzo[a]pyrene in rats.
- To assess the mutagenicity of the parent compound and its biliary metabolites.
Main Methods:
- Rats were administered 6-hydroxymethylbenzo[a]pyrene intraperitoneally.
- Biliary excretion was monitored over 6 hours.
- Mutagenicity was tested using the Ames Salmonella/microsome assay with and without metabolic activation (S9, beta-glucuronidase).
Main Results:
- Approximately 40% of the administered dose was excreted in bile within 6 hours, primarily as glucuronide and sulfate conjugates.
- Unchanged 6-hydroxymethylbenzo[a]pyrene was minimally excreted.
- The parent compound was mutagenic with S9 activation.
- Bile samples containing metabolites were mutagenic when incubated with beta-glucuronidase and/or S9.
Conclusions:
- Biliary metabolites of 6-hydroxymethylbenzo[a]pyrene can be activated to mutagenic species.
- This metabolic activation pathway may contribute to the carcinogenicity of 6-hydroxymethylbenzo[a]pyrene.