AbstractTaurine may act as an antioxidant, preventing development of inflammatory response and morphologic alteration in lungs of hamsters exposed to nitrogen dioxide. It may bind to plasma membrane reactive sites or stabilize specific molecules in cells inhibiting destructive processes. Localization of taurine is necessary in confirming its role. Hamsters were injected intraperitoneally with H3labeled taurine (0.1μCi/ml sp act 20 Ci/mmol) and sacrificed 1 hr or 18 hr after injection. Lungs were removed. fixed, and embedded in Epon. Control lungs were preparedto compare in vivo and in vitro labeling. Lung slices from untreated hamsters were incubated for 1 hr in McCoy 5A medium and then in medium containing H3taurine for 1 hr. Slices were washed in cold taurine for 1 hr, fixed, and embedded. One-μm sections were prepared for autoradiographic analyses. In situ and in vitro labeled tissues showed no differences in taurine distribution. All in vitro cells showed reater amounts of label than observed in the in vivo cells. In both cases, highest label concentrations were found in the airway epithelia, type II pneumocytes, and macrophages; to a lesser degree in endothelial cells. The lowest concentrations were found in the type I pneumocy tes. These data indicate that lung cells incorporate exogenous taurine. (The J Histotechnol17:29, 1994)