INDEPENDENT ANTIOXIDANT ACTION OF VITAMIN-E AND VITAMIN-C IN CULTUREDRAT HEPATOCYTES INTOXICATED WITH ALLYL ALCOHOL

The relationship between the metabolism of alpha-tocopherol (vitamin E ) and ascorbate (vitamin C) was examined in cultured hepatocytes intox icated with allyl alcohol. Alcohol dehydrogenase rapidly metabolizes a llyl alcohol to the potent electrophile acrolein. Acrolein depletes th e glutathione (GSH) content of the hepatocytes, thereby sensitizing th e cells to the constitutive flux of activated oxygen species. Suppleme ntation of the medium with 1 mu M alpha-tocopherol phosphate (alpha-TP ) prevents the 85% decline in cellular vitamin E seen after 16-18 hr i n culture. In cells supplemented with alpha-TP, allyl alcohol produced a concentration-dependent decline in the cellular content of alpha-to copherol, and these cells were more resistant to cell killing than hep atocytes not supplemented with alpha-TP. alpha-TP concentrations that raised the cellular alpha-tocopherol above the physiological level com pletely protected hepatocytes against the killing by allyl alcohol. In cells with physiological alpha-tocopherol, vitamin E declined within 30 min of exposure to allyl alcohol. This decrease paralleled the pero xidation of lipids, but preceded the decrease in cellular ascorbate. U nder these conditions, a decline in ascorbate correlated with the loss of cell viability. Cells supplemented with at least 3 mM ascorbate pr evented the decline in alpha-tocopherol. However, ascorbate acts as an independent antioxidant at these concentrations. In the absence of ki lling by allyl alcohol, the loss of cellular ascorbate did not depend on the presence or absence of cellular alpha-tocopherol. These data in dicate that vitamins E and C act as separate antioxidants and that asc orbate does not regenerate the tocopheroxyl radical in cultured rat he patocytes.