THE RELATIONSHIP BETWEEN FATTY-ACID PEROXIDATION AND ALPHA-TOCOPHEROL CONSUMPTION IN ISOLATED NORMAL AND TRANSFORMED HEPATOCYTES

The response of normal and transformed rat hepatocytes to oxidative stress was investigated. Isolated normal rai hepatocytes and differentiated hepatoma cells (the Fao cell line was derived from the Reuber H 35 rat hepatoma) in suspension were incubated with the ADP/Fe3+ chelate for 30 min at 37-degrees-C. Membrane lipid oxidation was assessed by measuring (i) free malondialdehyde (MDA) production by a high-performance liquid chromatography (HPLC) procedure, (ii) membrane fatty acid disappearance as judged by capillary gas chromatography, and (iii) alpha-tocopherol oxidation as determined by HPLC and electrochemical detection. The addition of iron led to increased MDA production in normal as well as in transformed cells, and to simultaneous consumption of polyunsaturated fatty acids (PUFA) and alpha-tocopherol. In addition, in Fao cells more alpha-tocopherol was consumed during lipid peroxidation while less PUFA was oxidized. Lipid peroxidation was lower in tumoral hepatocytes than in normal cells. This could be due to a difference in membrane lipid composition because of a lower PUFA content and a higher alpha-tocopherol level in Fao cells. During oxidation, Fao cells produced 1.5 to 2 times less MDA than normal cells, while in the tumoral cells the amount of oxidized PUFA having 3 or more double bonds was 7 to 8 times lower. Therefore, measuring MDA alone as an index of lipid peroxidation did not allow for proper comparison of the membrane lipid oxidizability of transformed cells vs. the membrane lipid oxidizability of normal cells.