Oxygen supply to contracting skeletal muscle at the microcirculatory level: diffusion vs. convection
Oxygen supply to contracting skeletal muscle at the microcirculatory level: diffusion vs. convection
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DOI：
10.1046/j.1365-201x.2000.00710.x
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发表时间：
2000-04-01
期刊：
影响因子：
--
通讯作者：
Pittman, RN
中科院分区：
文献类型：
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作者：
Pittman, RN
充足的氧气供应对所有细胞的正常功能至关重要。由于骨骼肌细胞有能力改变其氧气需求量超过一个数量级，从休息到剧烈收缩，重要的是要有机制，以确保氧气供应保持在足够的水平。微循环在这一过程中起着关键作用，因为这种复杂的血管网络的末端分支决定了灌注的分布以及扩散的结构框架。氧气供应取决于输送系统的对流和扩散组件的正常功能。对流负责通过血液的大量流动进行氧气的长距离快速运输，扩散是毛细血管和肌肉细胞之间短距离运输的有效机制。对流运输主要是由红细胞的运动，因为几乎所有的氧气在正常的红细胞压积进行内部，可逆地结合到血红蛋白。多年来，专门的技术，其中许多是基于视频的，已被开发用于活体显微镜，以测量量化毛细血管和较大的微血管，小动脉和小静脉中的对流和扩散所需的参数。我们对肌肉微循环中氧运输的大部分知识都属于静息状态，因为必须能够可视化感兴趣的结构，如微血管和肌肉细胞，并且在收缩期间发生的大的组织运动排除了在该时间内的测量。在静息肌肉中，已经发现小动脉是氧从循环中扩散的主要部位，其中氧被附近的肌细胞利用或直接扩散到附近的小静脉或毛细血管。还观察到相邻毛细管之间的扩散相互作用。在收缩肌肉中，在刺激期后立即观察到的微血管表现出对流（红细胞流动增加）和扩散（灌注毛细血管表面积增加）运输的增强。在解释实验研究的计算模型的使用是导致骨骼肌中的氧运输系统的基础过程的理解增加。
An adequate supply of oxygen is essential for the normal function of all cells. Because skeletal muscle cells have the ability to vary their oxygen demand by over an order of magnitude on going from rest to vigorous contraction, it is important that mechanisms be in place to ensure that the supply of oxygen is maintained at sufficient levels. Microcirculation plays a critical role in this process, as the terminal branches of this intricate network of blood vessels determine the distribution of perfusion, as well as the structural framework for diffusion. The oxygen supply depends on proper functioning of both the convective and diffusive components of the transport system. Convection is responsible for the long-range, rapid transport of oxygen by bulk flow of the blood and diffusion is the efficient mechanism for transport over the short distances between capillaries and muscle cells. Convective transport is dominated by the movement of red blood cells, as virtually all the oxygen at normal haematocrit is carried inside them, reversibly bound to haemoglobin. Over the years, specialized techniques, many of them video-based, have been developed for use in intravital microscopy to measure the parameters needed to quantify convection and diffusion in both capillaries and the larger microvessels, arterioles and venules. Most of our knowledge of oxygen transport in the microcirculation of muscle pertains to the resting condition, because one must be able to visualize the structures of interest, such as microvessels and muscle cells, and the large tissue movements that occur during contraction preclude measurements during that time. In resting muscle it has been found that the arterioles are the primary site of the diffusion of oxygen from the circulation, where the oxygen is utilized by nearby muscle cells or diffuses directly to nearby venules or capillaries. Diffusive interactions among neighbouring capillaries have also been observed. In contracting muscles, microvessels observed immediately following the period of stimulation exhibit enhancements of both convective (increased flow of red blood cells) and diffusive (increased perfused capillary surface area) transport. The use of computational models in the interpretation of experimental studies is leading to an increased understanding of the processes that underlie the oxygen transport system in skeletal muscle.