Effects of selenium and serum on selenoprotein W in cultured L8 muscle cells.

When rat L8 muscle cells were cultured to examine the effects of serum and selenium concentration on selenoprotein W levels and glutathione peroxidase (GPX) activities, no significant differences (P > 0.05) were found in selenoprotein W levels and GPX activities during differentiation. With three different forms of selenium, selenoprotein W levels and GPX activities were shown to increase in L8 myotubes cultured in media with these selenocompounds. Selenite was utilized more efficiently than selenocysteine for both selenoprotein W and GPX activity, but selenium as selenomethionine was less available. Both the protein content and mRNA levels for selenoprotein W were affected by the selenium content of the media. Northern blot data indicated that the expression of selenoprotein W mRNA increased significantly when L8 myotubes were cultured with selenium (P > 0.05). L8 myotubes cultured in 10% calf serum (CS) versus 2% CS with or without addition of 10(-8) M selenium indicated that the increase of selenoprotein W level in L8 myotubes cultured with higher serum concentration (10% CS) is due to the higher selenium concentration in media rather than serum itself.