Spectroscopic evidence for the generation of singlet oxygen in the reduced nicotinamide adenine dinucleotide phosphate-dependent microsomal lipid peroxidation system.

In the presence of Fe3+-ADP and NADPH, washed rat liver microsomes at 37 degrees and at pH 7.5 emitted ultraweak light with the peroxidative cleavage of endogenous lipid. The main light-emitting species of this system was analyzed spectroscopically in the visible region and estimated to be singlet oxygen. The addition of superoxide dismutase or catalase did not inhibit the light emission significantly. It is unlikely therefore that superoxide anion and OH are involved in the generation of singlet oxygen in the present system.