Valsartan alleviates atherosclerotic lesions in pulmonary arteries of rabbits via an endothelium-dependent mechanism

Abstract

Objective — Angiotensin II plays an important role in the pathogenesis of atherosclerosis.This study was designed to examine the effect of valsartan, an angiotensin receptor blocker, on atherosclerotic lesions in pulmonary arteries of rabbits with atherosclerosis induced by a high-cholesterol (HC) diet.

Methods — Male New Zealand rabbits were randomly divided into four groups: control, HC without valsartan, HC with 3 mg/kg/d valsartan, and HC with 10 mg/kg/d valsartan. Following 12 weeks of treatment, serum lipid profiles were determined. Pulmonary arteries were harvested and stained with Sudan IV for evaluation of atherosclerotic lesions. The middle lobes of the rabbit lungs were isolated, embedded in paraffin, and sectioned and stained with haematoxylin and eosin. Nitric oxide (NO) and endothelin-1 (ET-1) levels were determined in pulmonary arteries by nitrate reductase assay and radioimmunoassay, respectively.

Results — HC feeding altered serum lipid levels and induced atherosclerotic lesions in pulmonary arteries. Although 12 weeks of valsartan treatment failed to alter serum lipid levels, it significantly ameliorated HC-induced atherosclerotic lesions. Lesion areas, inflammatory cell infiltration, and occlusions of small arteries of lungs were reduced. Moreover, the endothelium-derived NO levels in pulmonary arteries were increased by valsartan treatment (10 mg/kg/d) compared to levels in the HC group. ET-1 levels were decreased by valsartan treatment compared to levels in the HC group. NO and ET-1 levels were not altered by valsartan at 3 mg/kg/d.

Conclusion — Our data demonstrates that HC diet-induced atherosclerotic lesions in rabbit pulmonary arteries can be ameliorated by treatment with valsartan, possibly through a NO and ET-1-dependent mechanism.

Key Words:

• Pulmonary artery
• atherosclerosis
• nitric oxide
• endothelin-1
• high-cholesterol diet