Significant differences in the cellular and molecular reactions of rat and hamster lung after quartz exposure.

Exposure of rats to high doses of quartz and other insoluble isometric particles can produce lung tumors. In contrast, after exposure of such particles in hamsters no tumor outcome has been observed. Recent studies have demonstrated that the tumorigenic effect of particles is closely linked to the induction of inflammatory processes and the subsequent formation and persistence of mutagenic oxidative DNA-modifications. Species-specific differences in sensitivity to particles should therefore be reflected in the molecular reaction of the lung cells. We exposed rats and hamsters to two different doses of quartz (0.3 mg, 1.2 mg/100 g body weight) by intratracheal instillation and characterized the dose-related pattern of pulmonary inflammation (neutrophil recruitment, TNF), toxicity (protein content, surfactant phospholipids), antioxidant defence (glutathione content), mutagenicity (8-oxoguanine, p53) and proliferation. Our results clearly demonstrate a significantly higher response of the rat to quartz exposure for all determined molecular and cellular parameters. Therefore the examination of these parameters in humans would contribute to the evaluation of the relevance of rats or hamsters as models to predict particle-induced human lung cancer risk.