Effect of dietary selenium on plasma selenoprotein P, selenoprotein P1 and glutathione peroxidase in the rat.

The purpose of this study was to determine the effect of dietary selenium on the abundance of selenium in plasma selenoprotein P, selenoprotein P1 and glutathione peroxidase. Weanling rats were provided water that contained 1.0, 0.1 or 0.01 ppm selenium and 75Se for 21 days. Gel filtration of denatured subunits was used to identify 75Se in the selenoproteins. Rats provided 1.0 ppm selenium accumulated 1.5 times more 75Se in liver cytosolic selenoprotein P1, but not in the two other selenoproteins, than did rats provided 0.1 ppm selenium. Most of the liver and blood selenium in rats provided 1.0 ppm selenium was insoluble and in an unknown chemical form. The tissue accumulation of unrecoverable selenium was apparently a response to the high dietary level of selenium. The proportion of selenium in plasma selenoprotein P, a putative selenium-transport protein, reflected the long-term selenium status of rats and varied from approximately 11-58% depending on the level of selenium supplementation. Turnover of selenium from this protein was affected by the dietary selenium of the rats. The results indicate that selenium incorporation into plasma selenoprotein P and selenoprotein P1 is affected by diet in ways that may reflect their importance to the rat.