Selenoprotein P: recent studies in rats and in humans

Purification of selenoprotein P from rat plasma has allowed detailed characterization of the protein from that species. Chromatographic studies have revealed the existence of at least two isoforms of the protein. One isoform is a truncated protein with termination of protein synthesis occurring at the second selenocysteine codon. Immunohistochemical studies have shown that the rat protein is associated with capillary endothelial cells in the liver, kidney, and brain. In vivo experiments were designed to study the relationship between selenoprotein P and lipid peroxidation. F2 isoprostanes were measured to quantitate the extent of lipid peroxidation caused by diquat. Using selenium-deficient rats supplemented with selenium, it was demonstrated that selenoprotein P appearance correlated with disappearance of diquat-induced lipid peroxidation. This finding is consistent with the protein serving to protect the plasma membrane from oxidative damage. Development of a radioimmunoassay to measure selenoprotein P has allowed assessment of the protein in humans. Measurements of the protein in selenium-deficient Chinese subjects indicated that it can be used as an index of selenium nutritional status in humans.