Chemical form of selenium greatly affects metal uptake and responses by cultured human lymphocytes

In this work, possible interference with functional activities of human lymphocytes after in vitro treatment with selenium was examined. Sodium selenite and selenomethionine compounds were tested in parallel, and their capability to inhibit or to increase the antibody production by lymphocytes was investigated. Furthermore, after incubation for 7 d, total cell-associated Se was measured by a fluorimetric method. The in vitro doses of Se employed in this study mainly reflect those measured in blood of individuals with different Se intake. Low doses of Se (0.5-2.0 microM) added either as sodium selenite or selenomethionine did not alter the secretion of antibodies. When Se was added at higher levels, instead, an inhibitory effect was found using selenite, whereas a progressive increase in immunoglobulin production was observed after exposure to selenomethionine. In both cases, modifications were detected at 5 microM (395 micrograms Se/L), and were significant at 10 microM (789 micrograms Se/L). A different trend between the two chemical forms was also observed with regard to Se uptake by cells. Interestingly, both Se uptake and cell sensitivity were influenced by the density of the cells in culture. Our data suggest that the biological effects of Se in mammalian systems are strongly influenced by its chemical form, and caution should be exerted to avoid toxic effects of selenium.