Granger H J, Goodman A H, Cook B H
Fed Proc. 1975 Oct;34(11):2025-30.
The functions and integrity of body tissues are critically dependent on an adequate oxygen supply. Because the transport of oxygen to the cells is intimately linked to the microcirculation, the concept of microcirculation-metabolism coupling has received much attention. In essence, the metabolic theory of intrinsic control of the microcirculation states that microvascular tone is locally modulated to maintain adequate oxygen levels in the parenchymal cells. We propose a two-component control system for the regulation of tissue O2 delivery in accordance with metabolic needs. A precapillary sphincter control mechanism maintains tissue PO2 by governing the number of perfused capillaries. Functional capillary density in turn determines surface area available for diffusion and capillary-to-cell diffusion distance. On the other hand, the arteriolar control system modulates local blood flow in accordance with parenchymal O2 utilization and thereby minimizes changes in capillary PO2 when the O2 availability/demand ratio is decreased. We propose that the precapillary sphincters are more sensitive to changes in tissue PO2 than are the flow-regulating arterioles. Consequently, for mild stresses, adequate tissue oxygenation is maintained mainly by precapillary sphincter control of diffusion parameters without the need for changes in blood flow. However, as metabolic stresses become greater, blood flow regulation becomes the dominant factor in the control of tissue O2 delivery. Thus, by working in concert, the local mechanisms regulating microvascular resistance and effective capillary density provide a wide margin of safety against the development of cellular hypoxia.
身体组织的功能和完整性严重依赖于充足的氧气供应。由于氧气向细胞的输送与微循环密切相关，微循环 - 代谢耦合的概念受到了广泛关注。本质上，微循环内在控制的代谢理论指出，微血管张力在局部受到调节，以维持实质细胞中足够的氧气水平。我们提出了一种双组分控制系统，用于根据代谢需求调节组织的氧气输送。毛细血管前括约肌控制机制通过控制灌注毛细血管的数量来维持组织的氧分压。功能性毛细血管密度反过来决定了可用于扩散的表面积以及毛细血管到细胞的扩散距离。另一方面，小动脉控制系统根据实质细胞的氧气利用情况调节局部血流，从而在氧气供应/需求比降低时将毛细血管氧分压的变化降至最低。我们认为，毛细血管前括约肌比调节血流的小动脉对组织氧分压的变化更敏感。因此，对于轻度应激，主要通过毛细血管前括约肌对扩散参数的控制来维持足够的组织氧合，而无需改变血流。然而，随着代谢应激的增加，血流调节成为控制组织氧气输送的主导因素。因此，通过协同工作，调节微血管阻力和有效毛细血管密度的局部机制为防止细胞缺氧的发生提供了广泛的安全边际。
