Vasorelaxant effects of procyanidins on pulmonary artery in vitro / 中国组织工程研究

ABSTRACT

BACKGROUND: Procyanidins is a kind of polyphenol compounds in regnum vegetable, which is composed of different quantities of catechin and epicatechin. Studies show that procyanidins plays a role on protecting vascular endothelium, scavenging free radicals, resisting platelet aggregation, and reducing capillary permeability. Thus, procyanidins has obviously functions of reducing blood pressure, anti-oxidant activity, anti-edema, preventing coronary heart disease and atherosclerosis. OBJECTIVE: To study the vasorelaxant effect of procyanidins on pulmonic rings and its mechanisms. METHODS: Rabbit thoracic pulmonary arteries were isolated. Pre-contracted with noradrenalin (1×10-6 mol/L) and their responses to different concentrations of procyanidins (0.625, 1.25, 2.5 mg/L) were investigated. After removal of the endothelium of pulmonary artery smooth muscle, the effects of different signaling pathway inhibitors on procyanidins-induced relaxation, including nitric oxide synthase inhibitor Nω-Nitro-L-arginine (1×10-4 mol/L), methylene blue (1×10-5 mol/L), prostaglandin synthase inhibitor indomethacin (1×10-5 mol/L) and blockage of the adrenergicβ-receptor propranolol (1×10-5 mol/L), were also assessed. RESULTS AND CONCLUSION: (1) Procyanidins did not change the resting tension of rabbit’s pulmonic rings, but caused an obvious dose-dependent relaxation in 1×10-6 mol/L noradrenalin-precontracted pulmonic rings (r=0.69, P < 0.001). (2) The relaxant effect of procyanidins was significantly reduced by removal of endothelium or by treatment with either Nω-Nitro-L-arginine or methylene blue, but not by treatment with prostaglandin synthase inhibitor or blockage of the adrenergic β-receptor. (3) Procyanidins (20 mg/L) dropped the dose-effect curves of noradrenalin, KCl and on pulmonic rings denuded endothelium. Moreover, affinity index of noradrenalin, KCl and CaCl2 decreased (P < 0.01). (4) Procyanidins also inhibited the vasoconstriction caused by noradrenalin in the first phase, but had no impact on the constriction induced by CaCl2 in the second phase. (5) Procyanidins has an endothelium-dependent vasorelaxation on isolated rabbit’s pulmonic rings, which is possibly mediated by nitric oxide/cyclic guanosine monophosphate pathways. Procyanidins blocked receptor-operated and voltage-dependent calcium channels to reduce intracel ular Ca2+, and induced vasorelaxation.