Graduate Thesis Or Dissertation
 

The effect of selenium on chemical carcinogenicity in the rat

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3484zk399

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  • One hundred and fifty-one weanling rats of both sexes were fed control diets or diets containing 160 ppm diethylnitrosamine (DEN) or 150 ppm N-2-fluorenyl-acetamide (FAA). The carcinogen level was calculated so that the LD₅₀ should be achieved at about 17 weeks. Each carcinogen treatment was incorporated with three different diet levels of supplemental selenium (0, 0.2 and 2 ppm) in order to evaluate the protective potential of selenium against carcinogenicity. The two control diets contained 0 ppm and 2 ppm selenium and served not only as a control but also to evaluate the function of selenium as an essential trace element involved in growth. Weekly weights and feed consumption were recorded and the data compared among the eight treatment groups. The rats were necropsied upon death and liver, lung and tumors were excised and subjected to histological evaluation for neoplasia. In an attempt at a status evaluation control several rats were killed from each control group and from each group containing the various selenium levels for that particular carcinogen. This exercise was performed when half of the rats died from a carcinogen group not containing selenium in the diet. This procedure has repeated when all the animals of a group died (0 Se/DEN only). The DEN diets were more palatable than the FAA diets. The level of selenium in the respective diets had no real influence upon consumption, except for the control diets. The consequence of this was that the rats on DEN were exposed to more carcinogen than those on FAA. All DEN animals and all FAA males were essentially free of peripheral carcinomas. Mammary carcinomas were common in FAA females with a metastatic state the rule. Selenium appeared to provide protection against tumors when included in the DEN groups. Incidence was reduced at least 20 per cent with selenium; the reduction was most apparent in the females. The protective action of selenium did not present itself in those groups exposed to FAA.
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