The redoxsensitive behaviour of selenite in presence of reactive oxygen species

From extensive research over the last decade it has been known that seleniu m is essential as necessary component of selenoaminoacids and of specific e nzymes. Among others, the redoxpair GSH/GSSG is closely connected with anti oxidative processes. Moreover it inhibits and/or activates molecular key re actions with the involvement of various small reactive O- and N-species. We investigated the direct interaction of selenite with components of the r espiratory burst of human blood cells, considering the redoxamphoterie of a lkali-selenite. Selenite tend to redox-disproportation depending on the pH- value. Whether selenite leads to oxidation or reductation is dependent not only on the pH-value, but also on the redox-potential of the reaction partners. In in-vivo adapted in-vitro conditions (ph=7.4, mu molar concentrations of re action partners) we observed the following results: 1. SeO32- is not oxidiz ed by H2O2/NO or triplet-oxygen, when the oxidatives are applied alone; 2. SeO32- is quantitatively oxidized from SeO42- by the combination H2O2/NO2- or O-2(-)/NO; 3. SeO32- is semiquantitatively oxidized by singlett oxygen t o SeO42-. The composition of reaction products was measured by Se-77-NMR-spectroscopy . The reactive intermediate product for the 2. reaction should be peroxynit rite (HOONO). One cannot rule out the possibility that HOONO reacts on a la rge scale with H2O2 to singlett oxygen. Subsequently singlett oxygen oxidiz es selenite. The pathophysiological impact of singlett oxygen in processes like arterios clerosis is now being investigated. It has been supposed, that singlett oxy gen in participating in processes of lipid peroxidation in vivo. Further in vestigations have to show to what extent selenite is effective as direct O- 1(2)-scavanger.