[Bio-effects of nano-TiO2 on lungs of mice]

To evaluate the acute lung toxicity of intratracheally instilled nano-TiO2 in Kunming mice, healthy adult male Kunming mice were randomly grouped by their body weight (5 mice in each group). The lungs of mice were intratracheally instilled with 1 or 10 mg/kg x bw of nano-TiO2. The control group was intratracheally instilled with the same volume of physiological saline. After 1 d, 7 d, 14 d and 28 d of exposure, the bronchoalveolar lavage fluid (BALF) and lung tissue were collected. The indices of BALF were examined. Lung tissues were assess histopathologically. The results showed that all indices of 10 mg/kg x bw groups were obviously higher than those of the control group and the group of nano-1 mg/kg x bw, respectively. Activities of lactate dehydrogenase (LDH) on the 1st, 7th, 14th and 28th day post-exposure (pe), the amounts of malodialdehyde (MDA) on the 1st, 7th and, 14th day pe and total protein (TP) on the 1st and 7th day pe as well as the amounts of leukocyte on the 1st and 7th day pe of 10 mg/kg x bw groups were significantly different as compared with controls (P < 0.05). There were no obvious changes observed in the activity of alkaline phosphatase (ALP) within groups (P > 0.05). Histopathological examination revealed that the lungs of 10 mg/kg x bw groups presented marked increase in pulmonary inflammation. Many TiO2 particles were still clearly found in the interstitium at 28 days pe. In contrast, low-dose instillation put forward a low risk potential for producing adverse effects on pulmonary health. We conclude that the inflammatory reaction gradually ceased after 28 days. Under the same experimental condition, the effect of lung injury was severer in high-dose nano-TiO2 than in low-dose nano-TiO2.