Huang A H, Feigl E O
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
Circ Res. 1988 Feb;62(2):286-98. doi: 10.1161/01.res.62.2.286.
The hypothesis that alpha-adrenergic coronary vasoconstriction helps maintain a uniform transmural distribution of myocardial blood flow during exercise was tested in dogs. Carotid artery loops were surgically constructed and a splenectomy performed three weeks prior to study. On the day of study, the dog was anesthetized briefly (fentanyl and nitrous oxide) for percutaneous catheterization, and alpha-receptors in one myocardial region were blocked with phenoxybenzamine (0.25 mg/kg) infused selectively into the left circumflex coronary artery. Recirculation of phenoxybenzamine was minimized by drainage of coronary sinus outflow during the infusion. After the dog recovered from the anesthesia, regional blood flow was measured at rest and during graded treadmill exercise with the microsphere technique calibrated by reference blood samples. Average transmural flow was limited by alpha-vasoconstriction and was less in the region where alpha-receptors were intact than in the region where they were blocked, as has been described by others. The ratio of inner layer myocardial blood flow to outer layer flow was better maintained in the region with alpha-receptors intact than in the region with alpha-receptors blocked when myocardial oxygen consumption was 150 microliter/min/g or greater (p less than 0.001). Even though average transmural flow was limited by alpha-receptor activation, inner layer myocardial blood flow was greater in the region with alpha-receptors intact than in the region with alpha-receptors blocked when myocardial oxygen consumption was 500 microliter/min/g or more (p less than 0.05). In conclusion, adrenergic coronary vasoconstriction mediated by alpha-receptors helps to maintain a uniform transmural distribution of myocardial blood flow during exercise in spite of limiting average transmural flow.
在犬类中测试了α-肾上腺素能冠状动脉血管收缩有助于在运动期间维持心肌血流均匀跨壁分布的假说。在研究前三周通过手术构建颈动脉环并进行脾切除术。在研究当天，犬只短暂麻醉（芬太尼和一氧化二氮）以进行经皮导管插入术，通过选择性注入左旋冠状动脉的苯氧苄胺（0.25mg/kg）阻断一个心肌区域的α受体。在注入过程中通过冠状窦引流使苯氧苄胺的再循环最小化。犬只从麻醉中恢复后，使用通过参考血样校准的微球技术在静息和分级跑步机运动期间测量局部血流。如其他人所描述的那样，平均跨壁血流受α血管收缩限制，在α受体完整的区域比在α受体被阻断的区域要少。当心肌耗氧量为150微升/分钟/克或更高时，α受体完整区域的内层心肌血流与外层血流的比率比α受体被阻断的区域维持得更好（p<0.001）。尽管平均跨壁血流受α受体激活限制，但当心肌耗氧量为500微升/分钟/克或更高时，α受体完整区域的内层心肌血流比α受体被阻断的区域更大（p<0.05）。总之，由α受体介导的肾上腺素能冠状动脉血管收缩有助于在运动期间维持心肌血流的均匀跨壁分布，尽管它会限制平均跨壁血流。
