Spin trapping of free radicals during hepatic microsomal lipid peroxidation.

We have used spin-trapping techniques to identify radical species formed during the NADPH-stimulated peroxidation of rat hepatic microsomes. Using 5,5-dimethyl-1-pyrroline-1-oxide, we have confirmed the presence of substantial quantities of superoxide but found evidence for the formation of only small quantities of hydroxyl radical. Use of the spin traps N-tert-butyl-alpha-4-pyridylnitrone-1-oxide and 2-methyl-2-nitroso-1-propanol have allowed us to determine that lipid peroxyl radicals are the predominant "lipid-type" radical found in peroxidizing microsomes under aerobic conditions. These data suggest that microsomal lipid dienyl radicals react with molecular oxygen at near diffusion-controlled rates.