Objective To explore the change of type Ⅰ and type Ⅲ collagen and IL-12 in the lung of rats after exposure to rare earth neodymium oxide dust at different time points.

Methods One hundred and twenty five healthy adult male SD rats (SPF grade), weighted (200±16) g, were randomly divided into a dust exposure group and a control group. The dust-exposure model was established by tracheal non-exposure intubation perfusion. The dust exposure group was treated once with a dust suspension containing 0.8 mL (50 mg/mL) of rare earth neodymium oxide; and the control group was treated with 0.8 mL of normal saline solution. Fifteen rats in the dust exposure group and 10 rats in the control group were killed at 3, 7, 14, 21 and 28 days after exposure. The content of IL-12 in the supernatant of bronchoalveolar lavage fluid (BALF) was detected by ELISA. The lung tissue was dyed with Sirius red and HE; type Ⅰ and type Ⅲ collagen fibers were quantified by using image-Pro Plus Version 4.5 for Windows TM image analysis system.

Results The levels of type Ⅰ and type Ⅲ collagen were increased significantly during the process of pulmonary fibrosis induced by rare earth neodymium oxide dust; type Ⅰ collagen hyperplasia was predominant in the early period of dust-exposure. The levels of type Ⅰ and type Ⅲ collagen in the exposure group were significantly higher than those in the control group (P < 0.05). Inflammation was the early change in lung tissue confirmed by pathological observation after exposure to dust, and there was a trend of increasing inflammation with the extension of time after exposure. The content of IL-12 in the supernatant of BALF was declined first and then climbed up; the minimum value was at the seventh day after exposure and then was increased, but the content was higher than that in the control group (P < 0.05).

Conclusions The level of type Ⅰ and type Ⅲ collagen was increased significantly in the process of pulmonary fibrosis induced by rare earth neodymium oxide dust, and the distribution was wide. Meanwhile, a high expression of IL-12 was observed in the supernatant of BALF, which indicated that the change of IL-12 was closely related to the occurrence and development of pulmonary fibrosis in rats induced by rare earth neodymium oxide dust.