MEMBRANE LIPID-FREE RADICALS PRODUCED FROM L1210 MURINE LEUKEMIA-CELLS BY PHOTOFRIN PHOTOSENSITIZATION - AN ELECTRON-PARAMAGNETIC-RESONANCESPIN-TRAPPING STUDY

We have detected membrane lipid-derived free radicals from neoplastic cells subjected to Photofrin photosensitization. The presence of the p rooxidants iron or iron plus ascorbate in the L1210 cell system increa sed the intensity of the spin-trapped lipid radical electron paramagne tic resonance spectra and correspondingly decreased cell survival. In addition, raising the proportion of unsaturated lipids in the cell mem branes by supplementation of the growth medium with docosahexaenoic ac id increased lipid radical formation and decreased cell survival when the L1210 cells were subjected to Photofrin and light These data educe the hypothesis that the extent of radical generation as well as the e fficacy of photodynamic therapy can be increased when prooxidant condi tions, which enhance free radical processes, are present in conjunctio n with photosensitizers that target membrane lipids.