Effect of vitamin E on human glutathione peroxidase (gsh-px1) expression in cardiomyocytes

To determine the effect of vitamin E on cellular antioxidant enzymes, human ventricular cardiomyocytes were incubated with 200νM all-racemic-a-tocopheryl acetate for 14 d at PO2S of 150 and 40 mm Hg. Cellular Cu, Zn superoxide dismutase, catalase, and GSH-Pxl activities were measured. Although SOD and catalase activities were unaffected by a-tocopherol, GSH-Px1 activities increased (p < .0001) as much as twofold. This increase was independent of oxygen tension and selenium. The increase in GSH-Pxl activity became significant (p < .01) by day 4. A nonantioxidant analog of α-tocopherol, 200αM RRR-a-tocopherol methyl ether, did not affect GSH-Px 1 activities. Although GSH-Px1 mRNA levels mirrored the changes in enzyme activities, the de novo nuclear GSH-Pxl transcript synthesis was unaffected by α-tocopherol. Because the increase in GSH-Px1 activities also occurred after cellular a-tocopherol levels had plateaued, the above results were most consistent with posttranscriptional stabilization of GSH-Pxl mRNA by α-tocopherol or an a-tocopherol-related metabolic product.