Abstract: ObjectiveTo explore subchronic pulmonary toxicity of nano-sized calcium carbonate in rats.MethodsThirty-two male rats were randomly divided into negative control group and three experimental groups exposed to 0.8,4,and 20mg/ml nano-sized calcium carbonate.The rats were instilled with physiological saline and different doses nano-sized calcium carbonate once a week for five weeks through tracheal injection method.The indices in bronchoalveolar lavage fluid (BALF)and lung tissue were determined,including lactate dehydrogenase(LDH),alkaline phosphatase(AKP),acid phosphatase(ACP),superoxide dismutase(SOD),and malonaldehyde(MDA).The pathological changes in the lung of the rats were also observed.ResultsThe level of LDH in 20mg/ml nano-sized calcium carbonate group,ACP in 4,20 mg/ml nano-sized calcium carbonate group were all higher than those of the saline control group with statistically significant differences(P=0.046 and P=0.002).The activities of AKP,SOD and the content of MDA of the lung were not significantly different among the groups.Pathological observation showed that the bronchus and alveoli of the rats in three nano-calcium carbonate groups were damaged in different degree.The infiltration of lympholeukocyte and heterophil granulocyte,the proliferation of interstitial fibrocyte were also observed.ConclusionNano-sized calcium carbonate may induce subchronic pulmonary toxicity in rats.