Baran K W, Bache R J, Dai X Z, Schwartz J S
Department of Medicine, University of Minnesota, Minneapolis.
Circulation. 1992 Mar;85(3):1139-45. doi: 10.1161/01.cir.85.3.1139.
Exercise-induced dilation of coronary resistance vessels is limited by alpha-adrenergic mechanisms. However, the effect of alpha-adrenergic mechanisms on large coronary arteries during exercise is not known.
In the present study, sonomicrometry was used to measure circumflex coronary arterial diameter during treadmill exercise before and after alpha 1-adrenergic blockade with prazosin in eight instrumented dogs. Before infusion of prazosin, exercise caused a fall in coronary vascular resistance (2.1 +/- 0.4 to 1.6 +/- 0.2 units, p less than 0.05) and dilation of the circumflex coronary artery (4.66 +/- 0.37 to 4.79 +/- 0.34 mm, p less than 0.05). Intracoronary infusion of prazosin during exercise caused a further decrease in coronary vascular resistance (1.6 +/- 0.2 to 1.4 +/- 0.2 units, p less than 0.05) and a further increase in circumflex coronary arterial diameter (4.79 +/- 0.34 to 4.83 +/- 0.34 mm, p less than 0.05). Intracoronary infusion of vehicle without prazosin during exercise did not cause a further decrease in coronary vascular resistance or increase in coronary diameter. Prazosin caused no significant increase in heart rate, aortic pressure, or coronary blood flow. Therefore, both small coronary resistance vessels and large epicardial coronary arteries dilated during exercise and dilated further after alpha-adrenergic blockade.
This finding indicates that alpha 1-adrenergic activity during exercise limits dilation of both large and small coronary arteries.
运动诱导的冠状动脉阻力血管扩张受α-肾上腺素能机制限制。然而，运动期间α-肾上腺素能机制对大冠状动脉的影响尚不清楚。
在本研究中，对8只植入仪器的犬，在使用哌唑嗪进行α1-肾上腺素能阻滞前后，利用超声测量仪在跑步机运动期间测量左旋冠状动脉直径。在输注哌唑嗪之前，运动导致冠状动脉血管阻力下降（从2.1±0.4降至1.6±0.2单位，p<0.05）以及左旋冠状动脉扩张（从4.66±0.37增至4.79±0.34毫米，p<0.05）。运动期间冠状动脉内输注哌唑嗪导致冠状动脉血管阻力进一步下降（从1.6±0.2降至1.4±0.2单位，p<0.05）以及左旋冠状动脉直径进一步增加（从4.79±0.34增至4.83±0.34毫米，p<0.05）。运动期间冠状动脉内输注不含哌唑嗪的赋形剂未导致冠状动脉血管阻力进一步下降或冠状动脉直径增加。哌唑嗪未引起心率、主动脉压或冠状动脉血流量显著增加。因此，小冠状动脉阻力血管和大的心外膜冠状动脉在运动期间均扩张，且在α-肾上腺素能阻滞后进一步扩张。
这一发现表明运动期间α1-肾上腺素能活性限制了大、小冠状动脉的扩张。
