Influence of dietary fiber on DNA adduct formation in rat tissues.

The occurrence of DNA-adduct-like indigenous compounds (I-compounds) was examined in tissue samples of rats differing in their microbial state and diet with or without pectins of different degrees of esterification (DE). For 21 days groups of six germfree and ten conventional rats were each fed either pectin-free or with diets containing 7.5% of three differently esterified pectin preparations (pectin A: DE 92.6%; pectin B: DE 70.8%; pectin C: DE 34.5%). DNA was isolated from colonic mucosa, liver, lung, kidney and measured by the highly sensitive 32P postlabelling assay for DNA adduct analysis. In germfree animals I-compounds were detected in all tissue samples after feeding the low-esterified pectin C. Under the higher-esterified pectins, A and B, a weak adduct formation could be demonstrated only in the liver, but not in the colonic mucosa, lung, and kidney. In conventional animals DNA adducts were found in all samples of colonic mucosa with the highest intensity in the control group, followed by the low-esterified pectin C group, and a weak intensity under the higher-esterified pectins A and B. The experiments show a tendency to a higher number and intensity of spots in the germfree compared with the conventional rats, in rats with a pectin-free compared with the pectin diet, and under the low-esterified compared with the higher-esterified pectins.