The ability of the amino acid taurine to protect against ozone (10028156) induced oxidative injury was studied in rat alveolar macrophages. Alveolar macrophages obtained from male Sprague-Dawley- rats were exposed to 0 or 0.45 part per million ozone for up to 60 minutes (min) following pretreatment with 100 to 500 micromolar (microM) taurine added to the extracellular medium. The effects on cellular viability, resting and zymosan stimulated chemiluminescence used as a marker for reactive oxygen species generation, total ATPase and sodium, potassium dependent ATPase (Na,KATPase) activity, leakage of lipid peroxides, reduced glutathione (GSH), protein, and potassium ion (K+) into the extracellular medium, and intracellular and extracellular taurine concentrations were determined. Ozone exposure significantly decreased macrophage viability, resting and zymosan stimulated chemiluminescence, and total ATPase and Na,KATPase activity in a time dependent manner. Leakage of lipid peroxides, protein, GSH, and K+ into the medium was significantly increased in a time dependent manner. Intracellular taurine concentrations increased with increasing length of ozone exposure for up to 30min and then decreased thereafter. Extracellular taurine concentrations increased progressively with increasing length of ozone exposure. Adding taurine to the extracellular medium resulted in increasing intracellular taurine concentrations. Taurine enrichment countered the effects of ozone on viability, lipid peroxidation, total ATPase activity, and GSH leakage in a dose dependent manner. Taurine at 100microM significantly countered the effects on Na,KATPase activity and protein leakage. The authors conclude that taurine protects against ozone induced injury in rat alveolar macrophages. The protective effect of taurine is thought to reflect its being mobilized from intracellular stores to the free state in response to ozone exposure.