摘要Objective To investigate whether the silicotic process leads to the predominant extrahepatic ceruloplasmin (Cp) gene expression found within the plasma and lung tissue contributing to the significant increase.Methods The previous work of our research group demonstrated changes of ceruloplasmin (Cp) in rat lung tissue and alveolar macrophages during silicosis by electrophoresis analysis, radioimmunological assay and immunoflurescent technique. It is of interest to clarify the cause of elevation of Cp, particularly in the silicotic lung. Though Cp is mainly synthesized in the liver, recent studies have also demonstrated Cp synthesis in rat sertoli cells and human synovial tissue. Wistar male rats (180-220 g) were instilled intratracheally with 50 mg of silica (more than 97% of SiO2 and 95% of the silica particles with diameters less than 5 μm) suspended in 1.0 ml saline. Rats were killed for excising their lung and liver on the 21st day after instillation. Lung cells were harvested by repeated bronchial lavages with saline. Monolayer cells were cultured for 12-16 hours in the serum-free culture medium. Then the alveolar macrophages were collected for assay.Results Dot blotting results showed that Cp mRNA content increased in the liver as expected and was also detectable in the lung, with a nearly 2-fold increase compared with the normal rat lung in the normal group (saline injection). In situ hybrodization and Northern blotting revealed that the lung mesenchymal cells and the alveolar macrophages can express Cp mRNA in silicosis.Conclusions These data indicate that the lung is a prominent site of extrahepatic Cp gene expression during silicosis, thus suggesting that this protein may play a previously unknown role in pulmonary injury or repair.