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Mutagen excretion and cytochrome P-450-dependent activity in germfree and conventional rats fed a diet containing
E Overvik1, P Lindeskog, T Midtvedt
1Department of Medical Nutrition, Karolinska Institute, Huddinge University Hospital, Sweden.
Abstract:
To evaluate a possible role of the intestinal microflora in the metabolism of the highly mutagenic compounds formed in fried meat, conventional and germfree male AGUS rats were fed a semi-synthetic diet containing fried meat. Changes in mutagen excretion in urine and faeces over time were studied using the Ames Salmonella assay. The faecal and urinary extracts were separated by means of high-performance liquid chromatography (HPLC), and the mutagenicity of the collected fractions was determined. Cytochrome P-450 IA (IA1 and/or IA2) were detected by the use of antibodies with the Western blot technique, and the corresponding enzyme activities were measured in microsomes from the small intestine and the liver. A quantitative as well as qualitative difference in excretion of mutagens between germfree and conventional rats was observed. The total excreted of mutagenicity was significantly higher for the conventional than for the germfree rats, as a result of a higher faecal excretion of mutagens in the conventional animals. The HPLC separations of urinary and faecal extracts showed a different mutagenic metabolite pattern between the germfree and conventional rats. An increased activity of the cytochrome P-450-dependent enzyme ethoxyresorufin-O-deethylase was observed in the small intestine of conventional rats on the fried meat diet, whereas no effect of this diet was observed in the germfree rats. Similar results were obtained in immunoblotting experiments using a P-450 IA antiserum. The present study indicates that the excretion pattern and thus also the metabolism of compounds present in fried meat are affected by the germfree status.
Insights
The intestinal microflora significantly impacts the metabolism and excretion of mutagenic compounds found in fried meat. Conventional rats showed higher mutagen excretion than germfree rats, indicating microbial influence on these compounds.
Area of Science:
- Toxicology
- Microbiology
- Biochemistry
Background:
- Fried meat contains highly mutagenic compounds.
- The role of intestinal microflora in metabolizing these mutagens is not fully understood.
Purpose of the Study:
- To investigate the influence of intestinal microflora on the metabolism of mutagenic compounds in fried meat.
- To compare mutagen excretion and metabolism in conventional and germfree rats.
Main Methods:
- Rats (conventional and germfree) were fed a diet containing fried meat.
- Mutagen excretion in urine and feces was analyzed using the Ames Salmonella assay.
- High-performance liquid chromatography (HPLC) separated mutagens, and mutagenicity was determined.
- Cytochrome P-450 IA levels and enzyme activities (ethoxyresorufin-O-deethylase) were measured.
Main Results:
- Conventional rats excreted significantly more mutagenicity than germfree rats, primarily in feces.
- HPLC analysis revealed distinct mutagenic metabolite patterns between conventional and germfree rats.
- Fried meat diet increased cytochrome P-450-dependent enzyme activity in the small intestine of conventional rats, but not germfree rats.
Conclusions:
- Intestinal microflora plays a crucial role in the metabolism and excretion of mutagenic compounds from fried meat.
- The germfree status alters the metabolism and excretion patterns of these compounds.
- Gut microbiota influences the toxicological effects of dietary mutagens.