Dietary quercetin, immune functions and colonic carcinogenesis in rats.

Rats fed 100 mg/kg quercetin (QUE) daily for 7 weeks had significantly enhanced natural killer cell activity compared to their vehicle (VEH)-fed control. In contrast, rats fed 100 mg/kg QUE and treated with the colon carcinogen, azoxymethane had significantly reduced natural killer cell activity compared to their VEH-fed azoxymethane-treated control. There was no significant difference in natural killer cell activity between the two control groups. Antibody production and delayed-type hypersensitivity were not altered by QUE feeding in any treatment group. In vitro exposure of splenic natural killer cells to 1mM QUE significantly decreased natural killer cell cytotoxicity. Lower QUE concentrations produced a non-significant reduction in natural killer cell activity that was restored to control values at 1 x 10(-13)M QUE. The distribution, multiplicity and total number of colonic preneoplastic lesions, aberrant crypt foci, was not significantly different in the QUE-fed azoxymethane-treated rats when compared to azoxymethane-treated vehicle-fed rats at the conclusion of 7 week feeding period. We found no correlation between immune function and development of preneoplastic colon lesions in this study.