SELENOPROTEIN-P IN SERUM AS A BIOCHEMICAL MARKER OF SELENIUM STATUS

Some characteristics of a radioimmunoassay of selenoprotein P (a major selenoprotein in human serum) are described. Polyclonal antibodies ge nerated in rabbits were used and goat anti-rabbit-IgG antiserum was us ed as a second antibody. Depending on the concentration of selenoprote in P, 1-10 mu l of human serum were used in the assay. The relative st andard deviation for the concentration of selenoprotein P was 6.3% bet ween assays and 7.7% within assays. Different animal sera gave no sign ificant interference, indicating that the antibodies did not react wit h non-human analogues of selenoprotein P. No indication of cross-react ivity could be found concerning extracellular glutathione peroxidase ( another selenoprotein in serum). Addition of increasing amounts of nor mal human serum and partially purified selenoprotein P to the radioimm unoassay resulted in parallel curves. Incubation at 4 degrees C gave s omewhat higher binding of labelled selenoprotein P than incubation at room temperature. The epitope, recognized by the antibodies, was appar ently stable after storage of serum (in the frozen state for years, an d in the cold for months). No significant amount of selenoprotein P co uld be demonstrated in red blood cells, and analysis of haemolysed who le blood gave expected data. Investigations of selenium status in diff erent study groups indicated that in most cases the concentration of s elenoprotein P in serum was positively correlated to that of glutathio ne peroxidase and serum selenium. In an intervention study, where subj ects decreased their selenium intake to 50%, the Serum levels of gluta thione peroxidase and selenium decreased, but no significant decrease of selenoprotein P could be demonstrated. In conclusion, the data sugg est that selenoprotein P may be a valuable new biochemical marker of s elenium status, which may respond differently from selenium and glutat hione peroxidase under certain conditions.