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United States Department of Agriculture

Agricultural Research Service

Title: Selenium from High-Selenium Broccoli Does Not Induce Glutathione Peroxidase(gsh-Px) Mrna Production As Well As Selenite, But Is More Effective in Inhibiting Colon Carcinogenesis

item Finley, John
item Davis, Cindy
item Gregoire, Brian

Submitted to: Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2000
Publication Date: N/A

Technical Abstract: We have demonstrated that selenium (Se) inhibits the formation of chemically induced aberrant colonic crypt foci (ACF) or aberrant crypts (AC) in rats, and that the inhibition is dependent on the amount and chemical form of dietary Se. We also have reported that Se in broccoli is metabolized differently than Se salts (such as selenate) or seleno-amino acids (such as selenomethionine). The present study compared the ability of Se from high-Se broccoli or selenite to induce GSH-PX or selenoprotein W (SeW) mRNA and to inhibit formation of AC or ACF. Northern blot analysis was performed on mRNA from rats fed a Se-deficient diet or 0.2 or 2 ug/g Se as selenite or high-Se broccoli. SeW and GSH-Px mRNA in brain and testes was unaffected; however, there was less GSH-Px mRNA in the liver (p=0.0001) of rats fed high-Se broccoli than rats fed selenite. The ability of Se in broccoli to inhibit colon carcinogenesis was studied in rats fed diets with 0.2 or 2 ug/g Se as selenite (some selenite diets also contained broccoli, but the broccoli was low in Se) or high-Se broccoli for 3 weeks, given two injections of dimethyl hydrazine, and then fed the same diets for eight additional weeks. Colons of rats fed 2 ug/g Se as high-Se broccoli had only 51% as many AC (p=0.01), and only 55% as many ACF (p=0.02) as rats fed 2 ug/g Se as selenite. These data indicate that some of the differences noted in tissue accumulation of Se from broccoli may be a result of decreased mRNA abundance. Although Se from broccoli does not accumulate in tissues as well as selenite, it apparently is more effective in reducing chemically-induced ACF. The ACF-preventative effects of high-Se broccoli apparently are independent of the benefits of broccoli alone.

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