title: Interaction of vitamin C and selenium supplementation in the modification of mammary carcinogenesis in rats.
abstract: The objectives of this study were a) to compare the efficacy of inorganic and organic selenium compounds in protecting against mammary tumorigenesis induced by 7,12-dimethylbenz[a]anthracene [(DMBA); CAS: 57-97-6] in rats and b) to study the interaction of vitamin C with either selenite (inorganic) or seleno-DL-methionine (organic) in chemoprevention. Control Sprague-Dawley rats were fed a purified 5% corn oil diet containing 0.1 ppm selenium. Selenite or seleno-DL-methionine was added to the basal diet in concentrations of 2, 3, or 4 ppm starting 1 week after DMBA administration. The inhibitory response in mammary tumorigenesis with selenium supplementation was dose dependent. Both selenium compounds were found to be equally efficacious in prophylaxis, although at the 4-ppm level a slight reduction in growth was observed. In the second experiment, different concentrations of vitamin C (0.2, 0.5, and 1%) were tested. In general, there was no change with the two lower levels; but a slight, although insignificant, increase in tumor yield was detected in rats supplemented with 1% vitamin C in the diet. The interaction of 0.5% vitamin C with either selenite or seleno-DL-methionine (3 ppm) was studied in the third experiment. Results showed that the protective effect of selenite in tumorigenesis was nullified by vitamin C, whereas the chemopreventive action of seleno-DL-methionine was not affected. It is possible that selenite is reduced by vitamin C to elemental selenium and is therefore not available for uptake by tissues. This hypothesis was indirectly supported by tissue selenium measurements showing that 0.5 or 0.25% of vitamin C in the diet completely negated in blood, liver, and mammary gland the accumulation of selenium induced by 3 ppm of selenite supplementation. Lower levels of vitamin C (less than or equal to 0.1%) were found to have no effect on tissue selenium concentrations. Furthermore, the presence of 0.1% vitamin C in the diet no longer abolished the anticarcinogenic effect of selenite. This study suggests that high levels of vitamin C can interfere with the accumulation of tissue selenium and that an increased titer of this trace element in cells is essential for retarding tumor development.
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control*; D051381:Rats; D011919:Rats, Inbred Strains; D020887:Selenious Acid; D012643:Selenium / Q000008:administration & dosage* / Q000378:metabolism; D012645:Selenomethionine / Q000378:metabolism
chemical_list: D015127:9,10-Dimethyl-1,2-benzanthracene; D012645:Selenomethionine; D020887:Selenious Acid; D012643:Selenium; D001205:Ascorbic Acid