IN-VITRO EXPOSURE OF TRACHEOBRONCHIAL EPITHELIAL-CELLS AND OF TRACHEAL EXPLANTS TO OZONE

An in vitro system for exposing respiratory epithelial cells or explan t tissues to ozone has been developed and characterized. This system i s designed to generate and monitor consistent, reproducible levels of ozone, over a range of concentrations, in a humidified atmosphere, and to allow an exposure time of 24 h or longer. Based on chemical analys is, highly reproducible concentrations of ozone are delivered througho ut the chamber, with a coefficient of variation of < 5% between five r eplicate vials exposed to 0.5 ppm of ozone for 50 min. The viability o f cultured human tracheobronchial epithelial cells, as measured by the ability to oxidize a vital dye, and of rat tracheal epithelium as mea sured by total numbers of necrotic cells in tracheal explants, after o zone exposure was examined in this system. Responses of cultured cells to ozone exposure as measured by bioassay were consistent with the ob served low level of variability of ozone concentration between replica te incubation dishes or vials. Responses of cultured cells to ozone we re proportional to duration of exposure and inversely proportional to the volume of medium covering the cells. We conclude that this newly d eveloped in vitro exposure system will allow relatively simple and con venient exposure of cultured cells or organs to ozone or other gaseous agents under highly controlled and reproducible conditions.