Influence of Radix Astragali on nitric oxide and endothelin-1 in pulmonary tissue in hypoxemic pulmonary hypertension in rats

Abstract

To study the influence of Radix Astragali (RA) on pulmonary tissue endothelin-1 (ET-1) and nitric oxide (NO) in hypoxic pulmonary hypertension rats. Twenty one healthy male Wistar rats weighing 210-310 g were divided into three group at random with 7 in each. The rats in control group were raised in ordinary room condition; those in hypoxic group were raised in ordinary pressure hypoxic box [concentration of O(2) was (10.0 +/- 0.5)%] for 8 hours a day, for 30 days; those in RA group were raised in the same condition as hypoxic group and treated with an intraperitoneal injection of RA 8 g/kg per day. The rats in the control group and hypoxic group were given the same volume of intraperitoneal injection of normal saline. Mean pulmonary arterial pressure (mPAP), mean carotid artery pressure (mCAP) were measured via right cardiac catheterization, concentration of NO in pulmonary tissue was measured by radioimmunoassay. (1) The mPAP (mm Hg) (21.9 +/- 1.6) and ET-1 (pg/ml) (309.1 +/- 58.1) in hypoxemic group were significantly higher than those in RA group (16.2 +/- 0.8, 287.7 +/- 57.5) and control group (15.3 +/- 0.8, 241.1 +/- 52.5) (P < 0.01, < 0.05), but the difference between RA group and control group was not significant. (2) NO (micromol/L) in pulmonary tissue in hypoxemic group (6.5 +/- 0.3) was lower than that in RA group and control group (9.2 +/- 0.9), NO in RA group was higher than that in hypoxic group but lower than that in control group (P < 0.05). (3) There was no significant difference in mCAP among the three groups (P > 0.05). (4) Under electron microscope, the endothelial cells of arterioles of the lung tissue of control group were flat and had normal morphology. However, in the lung tissue of hypoxic group, there were proliferation, hypertrophy and swelling of endothelial cells of pulmonary medium and small arteries and plenty of mitochondria and endoplasmic reticula in cytoplasm. Chronic hypoxia can result in reconstruction and endothelial lesion in pulmonary arterioles of rats, elevation of mPAP and ET-1 in pulmonary tissue, and decrease of NO. Injection of Radix Astraglai can reverse the reconstruction of pulmonary vessels partially, regulate the concentration of ET-1 and NO in pulmonary tissue, which may have certain therapeutic effects on pulmonary arteriolar changes induced by hypoxia.