OBJECTIVETo investigate the dynamic changes in the expression of clara cell protein (CC16) and surfactant protein D (SP-D) in the lung tissues and bronchoalveolar lavage fluid (BALF) of silica-treated rats.

METHODSEighty-four Wistar rats were randomly divided into control group (n = 42) and silica group (n = 42). The silica group was subsequently divided into 3, 7, 14, 21, 28, and 60 d subgroups. The silicotic model was made by instilling silica suspension directly through the trachea into rat lungs. At 3, 7, 14, 21, 28, and 60 d after silica instillation, 8 rats in each group were sacrificed and their lung tissues and BALF were collected. The expression of SP-D and CC16 in lung tissues was detected by immunohistochemistry. Enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of SP-D and CCl6 in BALF.

RESULTSThe immunohistochemical assay indicated that CCl6 and SP-D were expressed in lung cells. The ELISA found that in 7, 14, 21, 28, and 60 d silica subgroups, the content of CCl6 in rat BALF was 8.14±0.70, 7.15±0.66, 7.00±0.69, 6.34 ± 0.59, and 5.27±0.49 ng/L, respectively; CCl6 expression decreased gradually with the silica exposure time prolonged, indicating a negative correlation (ra = -0.953, P < 0.01). Compared with the control group, all silica subgroups had significantly decreased CCl6 levels (P < 0.05). The content of SP-D in BALF was 12.20 ± 1.57, 14.41 ± 0.65, and 12.18 ± 0.74 ng/L, respectively, in the 7, 14, and 21 d silica subgroups, significantly higher than that in the control group (P < 0.05).

CONCLUSIONThe dynamic changes in SP-D and CCl6 protein levels in the lung tissues and BALF of rats could be induced by silica exposure and are related to silica exposure time. With the extension of silica exposure, CCl6 levels are gradually reduced, while the SP-D levels first increase and then fall.