Expression of Clara cell secretory protein in the lungs of rats exposed to silicon carbide whisker in vivo

Intratracheal instillation studies have shown that exposure to silicon carbide whiskers (SiCW), an asbestos substitute, produces pulmonary fibrotic changes, suggesting that SiCW might have fibrogenic potential. It has been theorized that Clara cell secretory protein (CCSP) plays a critical role in regulating the acute inflammatory response in the lung. The present study was conducted to investigate the time course of the expression of CCSP in lungs exposed to SiCW in vivo. Male Wistar rats were administered 2 mg or 10 mg of SiCW suspended in saline by a single intratracheal instillation and were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months of recovery time. The expression of CCSP was observed by reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot and immunostaining. Exposure to 10 mg of SiCW decreased in levels of CCSP mRNA at 3 days, 1 week, 1 month and 6 months following intratracheal instillation. The protein level of CCSP in SiCW-exposed rats was decreased at 1 day, 3 days and 1 month after a single instillation of 2 and 10 mg. These findings suggest that CCSP are involved not only in the acute injury but also in the chronic injury of the lung exposed to SiCW.