[Refractory ceramic fibers induced changes in serum Clara cell protein 16 and surfactant protein D levels in rats]

Objective: To explore the effect of refractory ceramic fibers (RCFs) on the serum Clara cell protein 16 (CC16) and surfactant protein D (SP-D) levels in Wistar rats. Methods: In October 2020, 96 healthy adult male Wistar rats were randomly divided into control group (equal volume of normal saline) , low-dose group (5 mg/ml RCFs) , medium-dose group (10 mg/ml RCFs) and high-dose group (20 mg/ml RCFs) , and subjected to non-exposure tracheal instillation. After intraperitoneal anesthesia, the rats were instilled with 200 μl of RCFs suspension or normal saline, once every 3 days for a total of 4 times. At 7, 14, 28, and 90 days after exposure, 6 rats were sacrificed by blood sampling through the abdominal aorta. The organs were separated, histopathological changes of lungs were observed and lung injury scores were performed. The contents of serum CC16 and SP-D were determined by enzyme-linked immunosorbent assay (ELISA) . Results: RCFs could cause inflammatory cells in rat lung tissues, widening of the lung septum and destruction of alveolar structure. 7 days after exposure, the lung injury scores of rats in each dose group were higher than control group, and the lung injury score of the high-dose group was higher than low-dose group (P<0.05) . 14 and 90 days after exposure, the lung injury scores of the medium-dose and high-dose groups were higher than control group (P<0.05) . 28 days after exposure, the lung injury score of the high-dose group was higher than control group (P<0.05) . 7 days after exposure, the serum CC16 and SP-D concentrations of rats in the medium-dose and high-dose groups were significantly higher than control and low-dose groups (P<0.05) . 28 days after exposure, the serum CC16 concentrations of rats in the low-dose and medium-dose groups were significantly lower than those of the control and high-dose groups (P<0.05) . After 90 days of exposure, the serum CC16 concentrations of rats decreased with the increase of the exposure dose (F=28.853, P<0.01) , and the concentrations of SP-D increased with the increase of the exposure dose (F=25.636, P<0.01) . Conclusion: RCFs exposure may cause certain damage to rat Clara cells and alveolar-capillary barrier. The severity of lung injury can be indirectly understood through the dynamic changes of serum CC16 and SP-D.