去甲肾上腺素缩血管作用对犬冠状血管舒张的限制

The Limiting Effect of α-Adrenergic Vasoconstriction on Canine Coronary Vasodilation Induced by Adenosine

在10只麻醉开胸犬的左前降支冠状动脉(LAD)恒流灌注,持续监测灌注压,并于冠脉内注入2.5mg心得宁以阻断心脏的β_1-肾上腺素能受体,观察去甲肾上腺素(NE,α-肾上腺素能刺激)对LAD内给予腺苷所致冠状血管舒张的限制作用。随着LAD内注入的腺苷量增加,冠状动脉阻力(R)咸剂量依赖性降低,分别为对照值的8.7％(2μg/min),20.6％(10μg/min)和28％(50μg/min)。而于LAD内再给予相同齐0量(6μg)的NE,则使不同剂量扩张的冠脉收缩,R成阶梯状增加,分别为对照值的17.4％(腺苷2μg/ml),23.2％(腺苷10μg/min)和34.1％(腺苷50μg/min),表现为隙苷引起的冠状血管扩张愈大,NE能刺激引起的缩血管作用愈强。这表明α-肾上腺素能缩血管作用可限制腺苷引起的冠状血管舒张,因而有助于保持冠状血管张力及其储备力。

This study examines the effects of α-adrenergic stimulation on coronary vasodilation induced by various doses of intracoronary adenosine. In anesthetized open chest dogs, the left anterior descending coronary artery (LAD) was perfused al constant flow and its perfusion pressure was measured. Practolol (2.5mg) was infused into the LAD to block β1-adrenergic receptors in myocardium. lntracoronary adeno-sine at increasing doses produced graded decreases in coronary vascular resistance by 8.7% (2μg/min), 20.6%' (10μg/min) and 28% (50μg/min) of control. The identical doses (6μg) of intracoronary norepinephrine produced increases in coronary vascular resistance by 17.4% (adenosine 2μg/min), 23.2% (adenosine 10 μg/min) and 34.1% (ade-nosine 50μg/min) of control when coronary vessels were dilated by increasing doses of adenosine, respectively. It is suggested that the constrictive effect of α-adrenergic stimulation can exert a limiting effect on adenosine-induced coronary vasodilation.