Activity of the Glutathione Peroxidase-2. Differences in the Selenium-dependent Expression between Colon and Small Intestine

Abstract

Background: Selenium (Se) is an essential element which is involved in various biological processes in nearly all tissues of animals and human, e.g. protection against oxidative stress in the cardiovascular system, and may play a role in cancer protection. It is incorporated in the proteome in the form of the genetically encoded amino acid selenocysteine, which is the characteristic component of the selenoproteins. Materials and Methods: We investigated the expression of the selenoenzyme GPx-2 which is predominantly present in the tissues of the gastrointestinal tract such as the small intestine and therefore named gastrointestinal glutathione peroxidase. Rats were fed with a Se-adequate or Se-deficient diet and GPx-2 was assessed by means of enzyme activity with respect to the Se concentration in tissues of the colon and small intestine. Se quantification was carried out by means of graphite furnace atom absorption spectrometry and 2D-gel electrophoresis was applied to investigate the expression of the proteins of the small intestine tissue samples. Results: Twenty-eight differences could be distinguished in the protein spot distribution of the 2D-gels of the homogenates. The GPx-2 activity in the Se-deficient rat colon samples was 6.8 fold lower than in the Se-adequate rats in contrast to 1.2 fold lower levels between the corresponding samples in the small intestine. Conclusion: This finding might explain the different susceptibility of the colon and the small intestine to cancer and support the theory of the protective effect of selenium in the gastrointestinal tract.