Fate of Pathologically Bound Oxygen Resulting from Inhalation of Labeled Ozone in Rats

Abstract

Inhaled ozone (O 3 ) reacts chemically with respiratory tract biomolecules where it forms covalently bound oxygen adducts. We investigated the fate of these adducts following inhalation exposure of rats to labeled ozone ( 18 O 3 , 2 ppm, 6 hr or 5 ppm, 2 hr). Increased 18 O was detected in blood plasma at 7 hr post exposure and was continuously present in urine for 4 days. Total 18 O excreted was -53% of the estimated amount of 18 O 3 retained by the rats during 18 O 3 exposure suggesting that only moderate recycling of the adduct material occurs. The time course of excretion, as well as properties of the excreted 18 O were determined to provide guidance to future searches for urinary oxidative stress markers. These results lend plausibility to published findings that O 3 inhalation could exert influences outside the lung, such as enhancement of atherosclerotic plaques.