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目的:研究去甲肾上腺素和异丙肾上腺素对冠状动脉环的舒张作用及其可能的作用途径。方法:采用离体实验方法,检测去甲肾上腺素和异丙肾上腺素对静息张力及氯化钾(KCl)预收缩冠状动脉的影响,研究两者对冠状动脉张力的作用及其可能的机制。结果:去甲肾上腺素和异丙肾上腺素对静息张力及KCl(40 mmol.L-1)预收缩冠状动脉环具有浓度依赖性舒张作用。去除内皮,用β受体阻断药普萘洛尔,β1受体抑制药阿替洛尔预处理后,均可明显减弱去甲肾上腺素和异丙肾上腺素诱导的舒张血管作用;用鸟苷酸环化酶抑制药亚甲蓝,一氧化氮合酶抑制药(L-NMMA),β2受体抑制药ICI-118551(10～5 mol.L-1)预处理后,血管舒张作用不能被阻断。α受体阻断药酚妥拉明预处理能增强去甲肾上腺素的舒张作用,对异丙肾上腺素引起的舒张无影响。结论:去甲肾上腺素和异丙肾上腺素是通过激活冠状动脉血管上的β受体(特别是β1受体)产生内皮依赖性的血管舒张作用,与NO-鸟苷酸环化酶途径无关。说明β肾上腺素能受体在猪冠状动脉血管平滑肌和血管内皮上有分布。
Objective: To study the relaxation effect of norepinephrine and isoprenaline on the coronary artery rings and its possible pathways. Methods: The effects of norepinephrine and isoproterenol on resting tension and precontracted coronary arteries of potassium chloride (KCl) were examined by in vitro experiments, and the possible mechanism of their effects on the tension of coronary arteries . Results: Norepinephrine and isoproterenol exerted a dose-dependent relaxing effect on resting tension and precontracted coronary artery rings of KCl (40 mmol.L-1). Removal of the endothelium, propranolol, a blocker of the beta-receptor, and pretreatment of the a1 receptor antagonist atenolol markedly attenuate noradrenaline and isoproterenol-induced vasodilatation; Vasodilation can not be inhibited by the pretreatment with acid cyclase inhibitor methylene blue, nitric oxide synthase inhibitor (L-NMMA) and β2 receptor inhibitor ICI-118551 (10-5 mol.L-1) Blocked. α receptor blocker phentolamine pretreatment can enhance the norepinephrine diastolic effect, isoproterenol-induced diastolic no effect. CONCLUSIONS: Norepinephrine and isoproterenol exert an endothelium-dependent vasodilatory effect by activating beta receptors on the coronary arteries, specifically the beta 1 receptor, regardless of the pathway of the NO-guanylate cyclase. This shows that β-adrenergic receptors are distributed in porcine coronary artery smooth muscle and vascular endothelium.