Ozone exposure generates free radicals in the blood samples in vitro. Detection by the ESR spin-trapping technique

Generation of free radicals in the reaction of ozone with blood samples and related salt solutions was investigated in vitro by using ESR spin-trapping technique with DMPO. In the reactions of low levels of ozone, a carbon-centered radical was spin-trapped with DMPO, giving rise to the 6-line ESR signal in both whole blood and blood plasma. In the blood plasma, DMPO-spin adduct of hydroxyl radical (DMPO-OH) was detected together with the spin adduct of carbon-centered radical. The present spin-trapping study demonstrates that, when exposed to ozone, 0.9% NaCl solution in the presence of DMPO gives rise to the formation of DMPO-OH. The addition effects of ethanol, which is a .OH scavenger, into the NaCl solution reveal that DMPO-OH is produced by the reaction of DMPO with both .OH and unidentified oxidants originated from the reaction of Cl- and ozone. Based on these observations, we consider that .OH is generated similarly in the blood plasma exposed to ozone. The ESR study of DMPO-spin adducts in the ozone-exposed aqueous solution of NaOCl indicates that Cl- reacts with ozone to give ClO-. Presumably, further oxidation of ClO- by ozone leads to the formations of .OH and the unidentified oxidants.