The capillary and sarcolemmal barriers in the heart. An exploration of labeled water permeability.
The capillary and sarcolemmal barriers in the heart. An exploration of labeled water permeability.
复制标题
心脏中的毛细血管和肌膜屏障。
作者：
C. Rose;C. Goresky;G. Bach
尽管心脏中血液和组织之间标记水的交换通常被认为是受血流限制的，但在多指示剂稀释实验中，相对于血管内参照，标记水的流出模式相对于用于解释渗透性较差物质转运的模型而言似乎是异常的。数据显示，在血管舒张以及输注毒性剂量的2,4 - 二硝基苯酚后，标记水流出曲线的形状发生变化，这使我们提出了一种标记水渗透的新模型，该模型包括毛细血管壁和肌膜的屏障。这个模型充分解释了流出曲线的形式，提供了与两个屏障的通透性相关的参数，并对细胞内与细胞间隙的比例进行了估算。动脉内输注足以导致心电图S - T段抬高的剂量的二硝基苯酚，发现可使肌膜水通透性降低一个数量级，但对毛细血管水通透性没有影响。我们得出结论，心脏中的水转运在毛细血管和肌膜处均受屏障限制，并且肌膜水通透性可能至少部分由一种对二硝基苯酚的作用敏感的结构介导，可能是一种蛋白质通道。由于惰性气体的流出模式与标记水相似，氧气分布也可能受屏障限制。
Although the exchange of labeled water between blood and tissue in the heart has usually been assumed to be flow-limited, the outflow patterns of labeled water, relative to intravascular references, in a multiple indicator dilution experiment, have appeared to be anomalous in terms of the models used to explain the transport of less permeable substances. Data showing a change in the shape of the labeled water outflow curve after vasodilation and after the infusion of toxic doses of 2,4-dinitrophenol led us to propose a new model for labeled water permeation which includes barriers at both the capillary wall and the sarcolemmal membrane. This model explains adequately the form of the outflow curve, provides parameters related to the permeability at the two barriers, and gives an estimate of the ratio of the intracellular to interstitial space. Dinitrophenol infused intra-arterially in a dose sufficient to cause S-T elevation in the electrocardiogram is found to reduce the sarcolemmal water permeability by an order of magnitude, but to have no effect on capillary water permeability. We conclude that water transport in the heart is barrier-limited at both the capillary and sarcolemmal membranes and that sarcolemmal water permeability is probably mediated at least in part by a structure sensitive to the effects of dinitrophenol, presumably a protein channel. Since the outflow patterns of inert gases resemble that of labeled water, it is possible that oxygen distribution is also barrier-limited.