[The effects of bilirubin concentration on laminin and epidermal growth factor expression in lung tissue and type II pneumocytes in smoking rats model].

Objective: To explore the effects of bilirubin on expression of laminin (Ln) and epidermal growth factor (EGF) in lung tissue and in type II pneumocytes (ATII) in smoking rats.

Methods: 36 healthy Wistar rats were randomly divided into three groups: a normal group, a smoking-induced emphysema model group (model group), and a bilirubin group (n = 12, for each group). According to XU San-lin method, rats both in the model group and the bilirubin group were exposed to smoke for a total of 6 months. Rats in the bilirubin group were pretreated with indirect bilirubin (20 mg.kg(-1).d(-1)) before exposed to smoke once a day. All animals were sacrificed six months later. ATIIwere isolated, purified and cultured. Ln in ATII culture medium was determined by radioimmunoassay (RIA). We detected Ln in lung tissue with indirect immunofluorescence technique and EGF with immunochemistry.

Results: In the model group, Ln content in ATII culture medium and in lung tissue [(5.0 +/- 0.3) mg/ml, 5.67 +/- 0.26] increased significantly compared with those in the normal group [(3.2 +/- 0.5) mg/ml, 2.01 +/- 0.74; P < 0.05, respectively]. In the bilirubin group, the two indexes [(3.9 +/- 0.7) mg/ml, 4.18 +/- 0.63] decreased significantly compared with those in the model group (P < 0.05, respectively), which was higher than the normal group (P < 0.05). Expression of EGF in lung tissue of the model group (0.43 +/- 0.09) increased significantly compared with that of the normal group (0.14 +/- 0.02; P < 0.05). The expression of EGF in the bilirubin group (0.34 +/- 0.03) decreased significantly compared with the model group (P < 0.05), which was higher than that of the normal group.

Conclusions: Bilirubin was shown to be able to promote the reconstruction of extracellular matrix by decreasing the expression of Ln and EGF in lung tissue and in ATII in the development of emphysema.