DIETARY SELENIUM INCREASES SELENOPROTEIN-W LEVELS IN RAT-TISSUES

Two experiments were conducted to evaluate the influence of dietary se lenium (Se) on tissue levels of selenoprotein W (Se-W) in rats, Se dep endent glutathione peroxidase (GPX) activity and Se levels were also d etermined for comparative measurements. In the first experiment, rats were fed a basal diet deficient in Se or supplemented with either 0.1 or 4.0 mg Se (as selenite) per kg diet for 6 wk, Se-W levels were sign ificantly higher in muscle, spleen and testes of rats fed 0.1 mg Se pe r kg diet compared to those fed the deficient diet (controls), and tho se fed 4.0 mg Se per kg diet had significantly higher levels in muscle , brain and spleen (P < 0.05) than those fed 0.1 mg Se per kg diet, No further increases, however, occurred in the tests, There was a signif icant increase (P < 0.05) of mRNA encoding Se-W in muscle with each in crease of dietary Se. In the second experiment rats were fed the basal diet or this diet plus 0.01, 0.03, 0.06, 0.1, 1.0, 2.0 or 4.0 mg Se p er kg diet, The levels of Se-W in muscle did not increase (P < 0.05) u ntil 0.06 mg Se per kg diet were fed to rats. A very marked increase ( P ( 0.05) occurred when 1.0 mg Se per kg diet was fed with no further increases with higher levels. There was a linear increase of Se-W in b rain (r = 0.89) and spleen (r = 0.98) with the Se concentration in the diet up to 0.1 mg Se per kg where a plateau was reached, The testes s howed a different pattern in that a very marked increase (P < 0.01) oc curred when only 0.01 mg Se per kg diet was fed where an inflection wa s reached. Except for muscle, GPX activities reached a plateau in all tissues when diets containing 0.06 to 0.1 mg supplemental Se per kg we re fed, The Se concentration in these tissues increased at a linear ra te with the Se concentration in the diets up to 0.1 mg Se per kg where it continued to rise al a different rate, The results indicate that i n rats, the regulation of Se-W by Se is different for various tissues and differs from that for GPX.