Biomarkers of Oxidative Stress Study IV: Ozone exposure of rats and its effect on antioxidants in plasma and bronchoalveolar lavage fluid

The objective of this study was to determine whether exposing rats to ozone would result in loss of antioxidants from plasma and bronchoalveolar lavage fluid (BALF). Additional goals were to compare analyses of the same antioxidant concentration between different laboratories, to investigate which methods have the sensitivity to detect decreased levels of antioxidants, and to identify a reliable measure of oxidative stress in ozone-exposed rats. Male Fisher rats were exposed to either 2.0 ppm or 5.0 ppm ozone inhalation for 2 h. Blood plasma and BALF samples were collected 2 h, 7 h, and 16 h after the exposure. It was found that ascorbic acid in plasma collected from rats after the higher dose of ozone was lower at 2h but not later. BALF concentrations of ascorbic acid were decreased at both 2 and 7 h post-exposure. Tocopherols (α-, δ-, γ-), 5-nitro-γ-tocopherol, tocol, glutathione (GSH/GSSG) and cysteine (Cys/CySS) were not further decreased, regardless of the doses and post-exposure time points used for sample collection. Uric acid was significantly increased by the low dose at 2h and the high dose at the 7 h point, probably due to the accumulation of blood plasma in the lung from ozone-increased alveolar capillary permeability. We concluded that measurements of antioxidants in plasma are not sensitive biomarkers for oxidative damage induced by the ozone and is not a useful choice for the assessment of oxidative damage by ozone in vivo.