Differences in selenium concentrations in target tissues and their relevance to its anticarcinogenicity.
Thompson H.J. | Ronan A.M.
At concentrations of dietary selenium (SE) that inhibit tumorigenesis in mammary gland or liver, a 12-15-fold difference exists between the Se concentrations in these tissues. This observation is difficult to reconcile with growing evidence of a common mechanism of anticarcinogenicity for various tissues protected by Se. Th examine this situation in detail, 48 female Sprague-Dawley rats were randomized and assigned to one of three treatment groups at 50 days of age. They were fed a diet containing either 0.1 microgram Se/g or the same diet supplemented with an additional 2.5 or 5.0 microgram Se/g. Se was provided as sodium selenite. Diets were fed for a 28-day period. At the end of this time, the experiment was terminated. Liver, lung, kidney and mammary gland were analyzed for Se by a fluorometric method. Liver and mammary gland DNA content also was determined. Se increased linearly with increased dietary Se in all tissues evaluated. Liver and mammary gland Se (microgram/g wet tissue) were significantly different from each other at every concentration of diet Se. However, the pattern of Se accumulation in these two tissues in response to different diet Se concentrations was essentially identical. Diet Se had no effect on tissue DNA content. Expression of liver and mammary gland Se per unit DNA eliminated between tissue differences in Se concentration indicating a similar SE/DNA ratio at a given level of dietary Se. These data point to the potential importance of intracellular Se content for expression of an anticancer effect. It is not known, however, if absolute Se concentration, generation of a particular specie(s) of Se or metabolism of Se per se, is the critical determinant for chemoprevention.
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