PDF(Pubmed)
Abstract：
The assumption that the coronary capillary blood flow is exclusively regulated by precapillary vessels is not supported by recent data. Rather, the complex coronary capillary bed has unique structural and geometric characteristics that invalidate many assumptions regarding red blood cell (RBC) transport, for example, data based on a single capillary or that increases in flow are the result of capillary recruitment. It is now recognized that all coronary capillaries are open and that their variations in flow are due to structural differences, local O2 demand and delivery, and variations in hematocrit. Recent data reveal that local mechanisms within the capillary bed regulate flow via signaling mechanisms involving RBC signaling and endothelial-associated pericytes that contract and relax in response to humoral and neural signaling. The discovery that pericytes respond to vasoactive signals (e.g., nitric oxide, phenylephrine, and adenosine) underscores the role of these cells in regulating capillary diameter and consequently RBC flux and oxygen delivery. RBCs also affect blood flow by sensing P O 2 and releasing nitric oxide to facilitate relaxation of pericytes and a consequential capillary dilation. New data indicate that these signaling mechanisms allow control of blood flow in specific coronary capillaries according to their oxygen requirements. In conclusion, mechanisms in the coronary capillary bed facilitate RBC density and transit time, hematocrit, blood flow and O2 delivery, factors that decrease capillary heterogeneity. These findings have important clinical implications for myocardial ischemia and infarction, as well as other vascular diseases.
摘要：
最近的数据不支持冠状动脉毛细血管血流完全由毛细血管前血管调节的假设。相反，复杂的冠状动脉毛细血管床具有独特的结构和几何特征，使许多关于红细胞（RBC）运输的假设无效，例如,基于单个毛细管或流量增加的数据是毛细管募集的结果。现在已经认识到，所有的冠状动脉毛细血管都是开放的，它们的流量变化是由于结构差异，当地O2需求和交付，和血细胞比容的变化。最近的数据表明，毛细血管床内的局部机制通过涉及RBC信号传导和内皮相关周细胞的信号传导机制调节流动，这些周细胞响应于体液和神经信号传导而收缩和松弛。周细胞对血管活性信号有反应的发现(例如，一氧化氮,去氧肾上腺素,和腺苷）强调了这些细胞在调节毛细血管直径以及RBC通量和氧气输送中的作用。RBC还通过感测P O
