OBJECTIVETo compare the pulmonary alveolitis and the early fibrosis of pulmonary fibrosis induced by quartz dust and bleomycin in rats, and investigate their mechanism.

METHODSThe female rats were divided into three groups: control group exposed to normal saline by the trachea; SiO2 group exposed to SiO2 by the trachea; BLM group exposed to BLM A5 by the trachea. Each half of the animals were sacrificed on the 7th and 14th day after exposure. The lungs of rats were collected to observe pulmonary alveolitis by HE staining and to observe fibrosis by saturated picric acid sirius red staining. The expression of tumor necrosis factor-alpha (TNF-alpha) and CD68 in pulmonary tissues were analyzed quantitatively by immunohistochemistry and image analysis system.

RESULTS(1) The alveolitis and pulmonary fibrosis of rats in both SiO2 group and BLM group were became more serious gradually over time, HE staining under light microscope showed that BLM group on the 7th day had the most obvious alveolitis (2.814 +/- 0.832), the saturated picric acid sirius red staining under polarized light showed that BLM group on the 14th day had the worst pulmonary fibrosis (1284.57 +/- 554.72), which were significantly higher than those (103.69 +/- 18.29 and 111.78 +/- 37.45) in control group and SiO2 group on the 7th day (P < 0.05). (2) The results of immunohistochemistry examination indicated that the expression (17.100 +/- 1.831) of TNF-alpha in the BLM group on the 7th day was significantly higher than those (0.451 +/- 0.441, 7.909 +/- 1.275 and 13.506 +/- 1.454) in control group, SiO2 group on 7th day and BLM group on 14th day (P < 0.05). The expression (22.778 +/- 2.512) of TNF-alpha in the SiO2 group on the 14th day was significantly higher than those in control group, SiO2 group on 7th day and BLM group on 14th day (P < 0.05). The expression (134.941 +/- 35.951) of CD68 in the SiO2 group on the 14th day was significantly higher than those in control group, SiO2 group on 7th day and BLM group on 14th day (P < 0.05).

CONCLUSIONThe early alveolitis of BLM-induced lung injury model was more serious than that of SiO2-induced lung injury model, and the fibrosis process of BLM-induced lung injury model was earlier than that of SiO2-induced lung injury model. TNF-alpha plays an important role in the course of both models, but macrophages is involved in SiO2-induced pulmonary in a more continuous way than in BLM-induced pulmonary fibrosis.