Alterations in Colonic Thymidine Kinase Enzyme Activity Induced by Consumption of Various Dietary Fibers

Dietary fibers may tend to enhance or inhibit chemically induced experimental colon cancer, depending on the particular fiber consumed. This study examined the relationship between colonic thymidine kinase enzyme activity and mucin histochemistry and the reported effects of various dietary fibers on chemically induced colon carcinogenesis. Fiber-supplemented diets containing fibers reported to inhibit (wheat bran) or enhance (guar gum, carrageenan) chemically induced colon carcinogenesis in the rat were selected. Four groups of male Fischer 344 rats consumed 10% wheat bran, 5% guar gum, 5% carrageenan, or fiber-free diets ad libitum for 4 weeks. At the completion of the treatment period, the distal 12 cm of colonic mucosa was scraped off and homogenized for determination of thymidine kinase activity, and a 0.5-cm section of midcolon was processed by the high-iron diamine/Alcian blue method for mucin histochemistry. Final animal weights did not differ significantly among groups. Thymidine kinase enzyme specific activity (μmole thymidine phosphate formed × 10⁶/min/mg protein, means ± SEMs) was not significantly different in the fiber-free, wheat bran, and guar gum groups (10.98 ± 1.50, 7.41 ± 1.09, and 9.11 ± 2.04, respectively) but was markedly elevated at 41.84 ± 4.65 in the carrageenan group (α < 0.001). Mucin histochemistry failed to reveal any significant differences among dietary groups.