Alleviation of hypoxic pulmonary vascular structural remodeling by L-arginine

Objective To explore the effect of L-arginine on hypoxic pulmonary vascular structural remodeling and its possible mechanisms. Methods Eighteen Wistar rats were randomly divided into three groups: the h ypoxia group, the hypoxia with L-arginine group and the control group. Pulm onary artery mean pressure was evaluated with right cardiac catheterization . Pulmonary vascular structural changes were also observed. Plasma concentr ation of nitric oxide (NO) was measured via spectrophotometry, and endothel in-1 (ET-1) mRNA expression in pulmonary artery endothelial cells was detec ted using in situ hybridization. Results The pulmonary artery mean pressure was significantly high in hypoxi c rats than in normal controls (20.33 +/- 2.18 mm Hg vs 15.38 +/- 1.05 mm H g, P < 0. 05). Microstructural and ultrastructural analysis revealed the de velopment of hypoxic pulmonary vascular structural remodeling in the hypoxi c rats. Meanwhile, the plasma NO concentration was markedly lower in the hy poxic rats than in controls ( P < 0. 05). The expression signals of ET-1 mR NA by pulmonary artery endothelial cells of hypoxic rats strengthened obvio usly. L-arginine ameliorated pulmonary hypertension (16.73 +/- 1.35 mm Hg v s 20.33 +/- 2.18 mm Hg, P < 0.05) as well as pulmonary vascular structural remodeling in the hypoxic rats in association with an increase in plasma NO concentration ( P < 0. 05) and inhibited ET-1 mRNA expression by the endot helial cells of pulmonary arteries. Conclusion L-arginine might play an important role in the regulation of hyp oxic pulmonary vascular structural remodeling and hypoxic pulmonary hyperte nsion. The mechanism is probably related to promoting NO production and, as a result, inhibiting ET-1 mRNA expression by pulmonary artery endothelial cells in hypoxic rats.