CYTOTOXICITY, PROOXIDANT EFFECTS AND ANTIOXIDANT DEPLETION IN RAT LUNG ALVEOLAR MACROPHAGES EXPOSED TO ULTRAFINE TITANIUM-DIOXIDE

In order to understand the pulmonary toxicity of ultrafine titanium di oxide (UF-TIO,) particles, various biochemical and chemical parameters were assayed in rat alveolar macrophages (AMs) and cell-free lavage f luid. Single intratracheal exposure of UF-TiO2 (2 mg per rat) caused c ytotoxicity to pulmonary AMs, An increase in the population of AMs cou ld be observed, followed by increased activities of lactate dehydrogen ase and acid phosphatase in cell-free lavage fluid. In addition, AMs s howed an adaptive response because the activities of glutathione perox idase, glutathione reductase, glucose-6-phosphate dehydrogenase and gl utathione S-transferase were increased in these cells. However, this e nhancement of antioxidant enzymes could not diminish the enhanced lipi d peroxidation and increased rate of hydrogen peroxide generation. The level of glutathione remained decreased in UF-TiO2-exposed rat AMs. T he data suggest that the induction of antioxidant enzymes by these cel ls for self-protection is not sufficient to cope against the toxic act ion of UF-TiO2, which may lead to oxidative stress. (C) 1998 John Wile y & Sons, Ltd.