Cytoprotection against lipid hydroperoxides correlates with increased glutathione peroxidase activities, but not selenium uptake from different selenocompounds

Cells cultivated under standard conditions were highly deficient in tocophe rol, selenium, and glutathione peroxidase (GPx) activities. We investigated whether and to what extent the addition of different selenocompounds to gr owth media would alter biochemical, physiological, and pathophysiological p arameters of cultured liver cells. Cellular uptake of selenium, GPx activit ies, and cytoprotection were measured and compared in human hepatoma cells (HepG2). Selenite and selenocystine were Se donors of high bioavailability (i.e., with these culture supplements, the increased Se uptake, induction o f GPx isoenzymes, and protection of treated cells from lipid hydroperoxides were well correlated). In contrast, selenium from selenomethionine was inc orporated into cellular proteins but had no effect on GPx activities or cyt oprotection. The data show that not all selenium donors provide selenium, w hich is bioactivated to act as antioxidant. Thus, cellular selenium content , in general, did not correlate with cytoprotective activity of this trace element. However, cellular GPx activities at different times, with differen t concentrations, and with different Se donors always correlated with prote ction from lipid hydroperoxides and may, thus, represent a more reliable pa rameter to define adequate Se supply.