LEVELS OF THIOBARBITURIC ACID REACTIVE SUBSTANCES AND THE CYTOCIDAL POTENTIAL OF GAMMA-LINOLENIC AND DOCOSAHEXAENOIC ACIDS ON ZR-75-1 AND CV-1 CELLS

To clarify the mechanism by which gammalinolenic acid (GLA) is more tumoricidal than docosahexaenoic acid (DHA), we have compared the incorporation of the respective exogenously added ethyl esters GLAe and DHAe into the phospholipids of tumorigenic ZR-75-1 and non-tumorigenic CV-1 cells relative to the ability of the cells to survive and to accumulate thiobarbituric acid reactive substances (TBARS). GLA and DHA were incorporated in the phospholipids to the same extent, but GLA disappeared more rapidly than DHA in both cell lines. GLAe induced about twice as much intracellular TBARS as DHAe in both cell lines, but killed ZR-75-1 cells four times more effectively than DHAe. DHAe induced 11-15 fmoles malondialdehyde-equivalents (MDA-eq)/cell in both ZR-75-1 and CV-1 cells, whereas GLAe induced 5-6 times more TBARS in ZR-75-1 cells (26-30 fmoles MDA-eq/cell) than in CV-1 cells (5-6 fmoles MDA-eq/cell). The results show that there is no difference in GLA and DHA incorporation into phospholipids, but that their metabolism differs in the two cell types. The data also suggest that the cytocidal potential is related to TBARS levels in a nonlinear fashion. The relationship between excess prostaglandin production and excessive cell death due to GLA is discussed.