Correlation between the size of the selenite-exchangeable metabolic pool and total body or liver selenium in rats

This study explored the quantitative relationship between the size of the selenite-exchangeable metabolic pool (WSe-EMP) and total body or liver Se in rats of varying age and past Se intake. We performed four experiments. In one, weanling rats were fed either a Se-deficient or Se-supplemented diet for 30 d, followed by measurement of WSe-EMP and total body Se. For the other experiments, rats were fed natural sources of Se without added selenite until adult age and then either subjected to acute Se restriction during the 7 d of measurements or maintained on a Se-sufficient diet. For the animals fed the selenite diet, the 7-d average ratio of WSe-EMP:total body Se (Se(end),0) was 0.370 +/- 0.009, which was not significantly different from the corresponding value (0.350 +/- 0.018, P greater than 0.05) for the Se-deficient group. When the group mean values of WSe-EMP were correlated with the corresponding mean values of Se(end),0 for all experiments, we obtained highly linear relations (r2 greater than 0.96). When WSe-EMP for each animal was correlated with the corresponding value of total body endogenous Se (Se(end)) or liver Se(end) (for t = 1 or 7 d), we found equally strong linear relations (r2 greater than or equal to 0.99). We concluded that WSe-EMP accurately reflected total body Se content or the Se content of such organs as liver, regardless of past Se intake, chemical form of Se or age and size of the animals.