Coronary arteriolar myogenic response in regulation of coronary circulation

冠状动脉血流有一个复杂的控制系统，包括三个主要机制：(1)当灌流压力改变时保持血流速度恒定的“自动调节”；(2)短时间冠状动脉闭塞后再灌注时的“反应性亢进”；(3)当心肌耗氧速率增加时，“负荷引起的整体流量增加”。这种冠状动脉血流控制被认为是通过内皮对代谢因素(腺苷、二氧化碳和氧分压)和控制因素等各种机制的“协同控制”。在这项研究中，我们聚焦于“心肌控制”，这是最近一个热门的研究主题。我们的主要目标是研究这种控制机制在冠脉血流控制条件下的作用，包括“自身调节”、“反应性高血症”和“负荷引起的血流速度增加”，然后阐明这些影响在诸如心肌缺血等病理条件下的意义。在这篇报告中，我们提出了…更多的是体内实验的结果，我们在这些实验中取得了很大的进步。用针尖探针式ccd显微镜观察心内膜下和心外膜下的微血管。将探头轻轻接触观察点，观察心外膜侧微血管。心内膜下侧者，通过左动脉附件将探头插入左心室，接触观察点，观察心内膜下侧。探针周围的血液用克雷布斯-林格溶液(37ﾟC)冲洗。心外膜下侧小动脉直径在收缩时增大，心内膜下侧小动脉直径在收缩时减小约20%。反应性充血时微动脉的反应，血流保持20s左右，直径最大约20s，约1min后恢复到初始值。心内膜下侧的血管恢复到初始值所需的时间比心外膜下侧的长。当房室传导阻滞引起舒张期延长时，冠状动脉内径随着主动脉压的降低而减小。而冠状小静脉则是先升高后趋于稳定。硝酸甘油增加了冠状动脉小动脉和小静脉的直径，也增加了直径在一个心脏周期内的变化幅度。较少

Coronary blood flow has a sophisticated control system including three major mechanisms : (1) "autoregulation" which keeps blood flow rate constant when perfusion pressure is changed, (2) "reactive hypermia" in reperfusion after short-time coronary artery occlusion, and (3) "an increase in bolld flow rate due to load" when myocardial oxygen consumption rate increases. This coronary blood flow control is considered "concerted control" of various mechanisms such as metabolic factors (adenosine, Pco2,and Po2) and control factors via endothelium. In this study, we focus "myocardial control" which has recently been a popular research topic. Our main goals are to study the effects of this control mechanism under the coronary blood flow controlling condition including "autoregulation," "reactive hypermia,) and "an increase in blood flow rate due to load," and then to clarity the significance of these effects during pathological conditions such as myocardial ischemia.In this report, we present … More the results for in vivo experiments in which we have made great advancement. A needle-probe CCD microscope was used to observe the microvessels in subendo- and subepi-cardial sides. The microvessels in the epi-cardial side was observed by gently contacting the probe to observation spots. Those in the subendo-cardial side was observed by introducing the probe through left arterial appendage into left ventricle and contacting it to observation spots. The blood around the probe was flushed with a Krebs-Ringer solution (37ﾟC). The diameter of the arteriole in the subepicardial side increased during systole while that in the subendocardial side decreased about 20 % during systole. as for the reaction of the arteriole at reactive hypermia by 20-sec blood flow hold, the diameter was maximum about 20 sec and returned to the initial value after about one min. The blood vessels in the subendocardial side needed longer time to return to the initial value than in those in the subepicardial side. When the prolonged diastole was induced by an AV block, the diameter of coronary arteriole decreased with decreasing aortic pressure. In contrast, that of coronary venule increased first and then reached a steady value. Nitroglycerine increased the diameter of both coronary arteriole and venule, and also increased the extent of the change in the diameter over a heart cycle. Less