Kazuo T. Suzuki, Kazuya Ishiwata and Yasumitsu Ogra
The metabolic turnover of selenoprotein P (Sel P) and extracellular glutathione peroxidase (eGPx) in plasma was examined by HPLC-ICPMS, with the use of enriched Se, [82Se]selenite. [82Se]selenite was injected intravenously into rats at a dose of 25 µg 82Se kg–1 body weight, and the concentrations of labeled 82Se and naturally occurring 77Se in the serum, liver and kidneys were determined in samples obtained 1, 3, 6, 9, 12, 18 and 24 h after the injection. The distributions of both exogenous (labeled) 82Se and endogenous (naturally occurring) 77Se 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 cellular 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 continued increasing after 6 h post-injection and then throughout the remaining observation period in the bloodstream. These observations demonstrated the rapid and efficient incorporation of Se into Sel P in the liver and excretion into the plasma followed by the slow and steady incorporation of Se into eGPx in the kidneys and excretion into the plasma, with a minimal response of cGPx to selenite injection.