Kono M, Morita S, Rubsamen R
Department of Anesthesiology, Teikyo University School of Medicine, Ichihara Hospital, Chiba, Japan.
J Cardiothorac Vasc Anesth. 1995 Oct;9(5):525-33. doi: 10.1016/s1053-0770(05)80135-1.
The contribution of alpha-adrenergic receptor subtypes in mediation of coronary vasoconstriction during ischemia remains controversial. This study investigated the effects of alpha-adrenergic subtypes blockade on regional myocardial function in a canine ischemic model.
Prospective, randomized, controlled trial.
Experimental animal laboratory in a university medical center.
Thirty-two adult dogs, weighing 13 to 22 kg.
The animals were prepared with pentobarbital, oxygen, enflurane and pancuronium. Two selective alpha 1-adrenergic antagonists (bunazosin, 50 micrograms/kg/min, n = 8, and prazosin, 25 micrograms/kg/min, n = 8) and the alpha 2-adrenergic antagonist (yohimbine, 15 micrograms/kg/min, n = 8) were administered after the partial occlusion of the left circumflex coronary artery (LCX) during beta-adrenergic blockade (propranolol, 1 mg/kg).
Myocardial systolic segment shortening (%SS) and a myocardial lactate extraction ratio (LER) were used as indices of regional myocardial and metabolic function. Compared with poststenotic condition, coronary blood flow of the LCX was increased by 123% with bunazosin and 138% with prazosin (p < 0.05, respectively). Both %SS and LER in the ischemic myocardium were significantly improved after treatment with both alpha 1-adrenergic antagonists (in the bunazosin group, %SS, 8.3 +/- 1.9 to 10.4 +/- 2.2%, p < 0.05; LER, -12.8 +/- 12.3 to 6.2 +/- 15.9%, p < 0.01; in the prazosin group, %SS, 8.5 +/- 1.6 to 10.3 +/- 1.9%, p < 0.05; LER, -10.2 +/- 5.7 to 3.6 +/- 10.2%, p < 0.05). In contrast, coronary blood flow of the LCX, %SS and LER were not different from poststenotic condition during alpha 2-adrenergic receptor blockade with yohimbine. The salutary effect of bunazosin was also observed after mechanically controlling for the afterload reduction produced by alpha 1-adrenergic blockade (n = 8). Prazosin and yohimbine were found to produce a significant increase in plasma norepinephrine levels in contrast to bunazosin, which had no significant effect.
These data indicate that alpha 1-adrenergic blockade increases coronary blood flow and improves regional myocardial function during myocardial ischemia.
α-肾上腺素能受体亚型在心肌缺血期间介导冠状动脉收缩中的作用仍存在争议。本研究在犬类缺血模型中探讨了α-肾上腺素能亚型阻断对局部心肌功能的影响。
前瞻性、随机、对照试验。
大学医学中心的实验动物实验室。
32只成年犬，体重13至22千克。
动物用戊巴比妥、氧气、恩氟烷和泮库溴铵进行准备。在β-肾上腺素能阻断（普萘洛尔，1毫克/千克）期间，左回旋支冠状动脉（LCX）部分闭塞后，给予两种选择性α1-肾上腺素能拮抗剂（布那唑嗪，50微克/千克/分钟，n = 8；哌唑嗪，25微克/千克/分钟，n = 8）和α2-肾上腺素能拮抗剂（育亨宾，15微克/千克/分钟，n = 8）。
心肌收缩节段缩短率（%SS）和心肌乳酸摄取率（LER）用作局部心肌和代谢功能指标。与狭窄后状态相比，布那唑嗪使LCX冠状动脉血流量增加123%，哌唑嗪使其增加138%（p均<0.05）。两种α1-肾上腺素能拮抗剂治疗后，缺血心肌的%SS和LER均显著改善（布那唑嗪组，%SS从8.3±1.9提高到10.4±2.2%，p<0.05；LER从-12.8±12.3提高到6.2±15.9%，p<0.01；哌唑嗪组，%SS从8.5±1.6提高到10.3±1.9%，p<0.05；LER从-10.2±5.7提高到3.6±10.
