Incorporation of selenium into selenoprotein P and extracellular glutathione peroxidase: HPLC-ICPMS data with enriched selenite

The metabolic turnover of selenoprotein P (Sel P) and extracellular glutath ione peroxidase (eGPx) in plasma was examined by HPLC-ICPMS, with the use o f enriched Se, [Se-82]selenite. [Se-82]selenite was injected intravenously into rats at a dose of 25 mu g Se-82 kg(-1) body weight, and the concentrat ions of labeled Se-82 and naturally occurring Se-77 in the serum, liver and kidneys were determined in samples obtained 1, 3, 6, 9, 12, 18 and 24 h af ter the injection. The distributions of both exogenous (labeled) Se-82 and endogenous (naturally occurring) Se-77 in serum, and supernatant fractions of the liver and kidneys were determined on a gel filtration column by HPLC -ICPMS. This dose was shown not to affect the constitutive levels of cellul ar GPx (cGPx), eGPx and Sel P. The labeled Se in Sel P increased soon after the injection, peaked at 6-9 h and then decreased, whereas that in eGPx co ntinued increasing after 6 h post-injection and then throughout the remaini ng observation period in the bloodstream. These observations demonstrated t he rapid and efficient incorporation of Se into Sel P in the liver and excr etion into the plasma followed by the slow and steady incorporation of Se i nto eGPx in the kidneys and excretion into the plasma, with a minimal respo nse of cGPx to selenite injection.