OBJECTIVETo observe the lung injury in rats induced by SiO₂ nanoparticles.

METHODSOne hundred and fifty SD rats were divided into five groups: the control group, the nanosized SiO₂ groups of 6.25, 12.5, 25 mg/ml, and the microsized SiO₂ group of 25 mg/ml, 30 rats each group. On the 7th, 15th, 30th, 60th and 90th day after exposure, six rats were sacrificed at each time point and the lung viscera coefficient, the pathological morphology and ultrastructure of lung were observed.

RESULTSAt each time point, the rat lung viscera coefficient of 25 mg/ml microsized SiO₂ and nanosized SiO₂ group were higher than the physiological saline group (P < 0.05), 25 mg/ml microsized SiO₂ group was higher than the same dose of nanosized SiO₂ group (P < 0.05); With longer duration of dye dust, lung viscera coefficient of 25 mg/ml microsized SiO₂ group and each dose of nanosized SiO₂ group were in time-effect relationship. Under light microscope we can see microsized SiO₂ group gradually formed cellularity nodules, and fused into fibrous nodules; At the early stage 25 mg/ml nanosized SiO₂ group occured focal alveolar macrophages and fibroblast proliferation and later fibrous connective tissue proliferated. Under TEM osmium lamellar corpuscle of type II alveolar epithelial cells were abnormal, and collagen and elastic fiber proliferated in mesenchyme of microsized and nanosized SiO₂ group.

CONCLUSIONNanosized SiO₂ particles after exposure can cause lung tissue injury in rat, and at the early stage it is showed inflammation, and later mainly characterized by pulmonary interstitial fibrosis differing from nodular lung fibrosis caused by microsized SiO₂, its ability to fibrosis is weaker compared with the same concentration of microsized SiO₂.