Objective To investigate the injury on lungs of the Institute for Cancer Research(ICR) mice after in tratracheally instilled multiwalled carbon nanotubes(MWCNTs), and provide a basis for evaluating its biological effects and exploring toxicity mechanisms.
Methods A total of 138 healthy adult ICR mice were randomly grouped by their body weight. Eight groups were employed. Phosphate-buffered saline (PBS)was used for solvent control and nothing for blank control with 5 mice in each group. Two dose groups (0.05 and 0.40 mg/kg body weight)of SiO2 were used as positive control with 6 mice in each group and four dose groups (0.05, 0.10, 0.20, and 0.40 mg/kg body weight)of MWCNTs as exposure groups with 6 mice in each group. Mice were intoxicated by intratracheal instillation once separately. On 1, 7 and 28 d after the instillation, mice were sacrificed and indices of lung injury in lung homogenate and bronchoalveolar lavage fluid (BALF)were determined respectively, and lung tissues were observed by histopathology.
Results The lung weight ratio of each exposure group showed a high tendency on the first day and then decreased, and resumed to the level of control on the 28 d group. The total protein, alkline phosphatase (AKP)and lactate dehydrogenase (LDH)in the BALF were relatively higher compared with the solvent control in the 1 d group and gradually decreased over the time. The lung weight ratios of the SiO2 control groups were lower than the MWCNTs groups on the 1 d and 7 d and then became higher on the 28 d. Histopathology observation showed that lungs of all exposure groups and positive control groups presented significant pulmonary inflammation and lung cell proliferation.Many MWCNTs were clearly found in some alveolar macrophages and bronchial epithelial cells in the exposure groups.
Conclusion Intratracheal in stillation of MWCNTs could induce injury on lungs of ICR mice, but the damage became less severe as time passed by. There were different lung injuries between MWCNTs and SiO2 groups, the possible mechanism of lung injury might be different.
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