DEPLETION OF URATE IN HUMAN NASAL LAVAGE FOLLOWING IN-VITRO OZONE EXPOSURE

Ozone, a strong oxidant present in summer smog, is thought to primaril y react with antioxidant molecules found in the epithelial lining flui d of the respiratory tract. In humans, as much as 40% of inhaled ozone can be removed in the nasal cavity where the major extracellular anti oxidant has been identified as uric acid. The present study was undert aken to examine urate/oxidant interactions in human nasal lavage fluid following in vitro exposure to ozone at concentrations relevant to th e U.K. Lavage fluid was collected from 8 volunteers using a modified F oley catheter which permits prolonged contact of isotonic saline with the anterior nasal cavity. Nasal lavage samples in multiwell plates we re exposed to ozone at concentrations of 50, 100 and 250 ppb. Samples were removed at intervals from 15 to 240 min following exposure and as sayed for uric acid depletion. Uric acid concentrations in the nasal l avage were found to fall from 8.52 (time zero) to 3.99 mu M, 0.05 and 0.07 mu M after 240 min at 50, 100 and 250 ppb ozone respectively. At a non-environmentally relevant ozone concentration of 1000 ppb, uric a cid was completely depleted after 60 min. Regression analysis showed a linear correlation between rate of loss of mate and ozone concentrati on (R(2) = 0.97). A novel, non-invasive technique is described to inve stigate antioxidant compromise and its importance in individual subjec ts. We conclude that uric acid in nasal lavage samples is scavenged by ozone in a dose and time dependant manner.