Regulatory effect of endogenous carbon monoxide on hypoxic pulmonary hypertension and pulmonary vascular structure

Objective To explore the role of endogenous carbon monoxide (CO) in regulating hypoxic pulmonary hypertension and pulmonary vascular structure. Methods Eighteen Wistar rats were randomly divided into control group, hypoxic group and hypoxic with ZnPP group. Pulmonary artery mean pressure of each rat was evaluated using right cardiac catheterization. Lung tissues were dyed with Weighert′s method. The percentage of each type of intra-acinar pulmonary arteries was measured. Relative media thickness (RMT) and relative media area(RMA) of the intrapulmonary arteries were observed. Collagen Ⅰand collagen Ⅲ expressions were detected by immunohistochemical assay. The expressions of type Ⅲ procollagen [Pro-α 1(Ⅲ) collagen] mRNA were detected by situ hybridization. Results mPAP was significantly increased in hypoxic group as compared with that of controls;and mPAP in hypoxic with ZnPP group was markedly increased compared with that of hypoxic group (P0.01).Percentage of muscularized artery,RMA and RMT of intra-pulmonary arteries were significantly increased in hypoxic group;ZnPP augmented mPAP and RMT and RMA markedly in hypoxic rats (P0.01). In hypoxic rats the expressions of collagen Ⅰ,collagen Ⅲ proteins and Pro-α 1 (Ⅲ) collagen mRNA in pulmonary arteries were increased significantly compared with rats of control group. ZnPP elevated expressions of collagen Ⅰ,collagen Ⅲ proteins and Pro-α 1 (Ⅲ) collagen mRNA obviously(P0.01). Conclusion Endogenous CO may act as a protective factor in hypoxic pulmonary hypertension and pulmonary vascular structure remodeling at least, which has partly involved in the regulation of CO in synthesis of collagen in pulmonary artery of hypoxic rats.