Some Comparative Aspects of Selenite and Selenomethionine Metabolism

Abstract

The different ratios of glutathione peroxidase (GPx) to selenium (Se) content in human erythrocytes as compared to those from animals are due to differences in the distribution of Se between the erythrocyte proteins, mainly GPx and hemoglobin (Hb). However, based on some rat experiments, this is probably not due solely to species differences but also to the dietary forms of Se consumed. When rats were fed diets with selenite as the Se source, essentially all of the Se was deposited with GPx, but when the source was selenomethionine, as supplied by high-Se wheat or selenized yeast, as much as 60% of the Se was deposited with Hb in the erythrocytes. Since the erythrocyte GPx activity is so low in comparison to the peroxidase activity of Hb, this creates a source of error in the assay of GPx in human blood, and thus this assay cannot be used to accurately assess Se status. When selenomethionine was the dietary source of Se for rats, significantly more Se was deposited in tissues (1.4 to 3.6-fold in liver, kidney, testis, blood, heart, and spleen), particularly the pancreas (8.5-fold) and muscle (10-fold), as compared to selenite as the Se source. Such data may be useful in designing experiments for testing the effectiveness of various Se compounds for cancer chemopreventive purposes.