Background: Many assays have investigated GPx activity but there are few reports of immunoreactive methods of GPx plasma determinations and their relationship with plasma selenium.
Methods: A cross-sectional analysis of selenium and GPx was carried out on 170 adults randomly selected from the electoral role. Blood samples were collected and analysed for plasma GPx using a commercial enzyme-linked immunosorbent assay (ELISA) kit and plasma selenium using magnetic sector ICP-MS. Further investigations of GPx level were carried out using one-dimensional (1D) and two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE).
Results: Plasma GPx was associated with plasma Se level (r(2)=0.24, P<0.0001). Mean (range) Se was 108.9 (67.4-268.0) microg/l. Mean (range) plasma GPx was 18.5 (3.8-43.8) microg/ml, significantly higher than the theoretical mean GPx of around 6.5-6.9 microg/ml based on ICP-MS results and the proportion of Se in intact GPx. GPx was higher in males than females and lower in current than non-smokers and ex-smokers. PAGE analysis of glycine dissociated ELISA wells revealed GPx as well as a number of unknown proteins with significant variability between high and low GPx samples.
Conclusions: Plasma GPx is correlated with Se status, however, there is considerable GPx variability between patients and ELISA methods appear to significantly overestimate true plasma GPx.