BIOMECHANICS OF SKELETAL-MUSCLE CAPILLARIES - HEMODYNAMIC RESISTANCE, ENDOTHELIAL DISTENSIBILITY, AND PSEUDOPOD FORMATION
BIOMECHANICS OF SKELETAL-MUSCLE CAPILLARIES - HEMODYNAMIC RESISTANCE, ENDOTHELIAL DISTENSIBILITY, AND PSEUDOPOD FORMATION
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DOI：
10.1007/bf02584425
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发表时间：
1995-05-01
影响因子：
3.8
通讯作者：
SCHMIDSCHONBEIN, GW
中科院分区：
文献类型：
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作者：
LEE, J;SCHMIDSCHONBEIN, GW
本研究的目的是探讨大鼠骨骼肌毛细血管的结构及其在较宽的跨壁压范围内的力学特性。将毛细血管固定在受控压力下，并用活体显微镜和电子显微镜进行研究。毛细血管管腔尺寸取决于局部跨壁压，在低跨壁压下具有不规则和部分塌陷的横截面，在升高的压力下具有圆形横截面。平均周向壁应力是周向拉伸的非线性函数。跨毛细血管压的升高用于增加暴露于管腔和基底膜的内皮表面积，而平均内皮厚度和细胞体积减小。随着内皮细胞的拉伸，内皮细胞中的囊泡数量和平均大小逐渐减少。囊泡和细胞表面上的膜面积测量的平衡表明，总膜表面在所有压力下是保守的，并且囊泡在内皮细胞的拉伸过程中变得展开。这表明，囊泡膜作为一个水库增加内皮细胞表面膜面积在毛细血管扩张。在正常或升高的毛细血管压力下，几乎没有发现内皮细胞形成伪足的证据。如果在自体血浆存在下将毛细血管跨壁压降低至零约10 min，则在不到10%的毛细血管切片中观察到伪足的有限证据。如果用plasmalyte灌注肌毛细血管并在低压下固定，则所有毛细血管均表现出伪足形成。此外，血浆蛋白阻止大多数伪足的形成。内皮伪足缺乏囊泡，形成片状突起。一旦伪足在低压下形成，它们就不能通过毛细血管透壁压的升高而容易地展开。伪足似乎由交联的肌动蛋白基质组成，可能对毛细血管中的血流阻力有很强的影响。这些结果可能与低压下的毛细血管血流有关。
The objective of this study was to investigate the structure of capillaries in rat skeletal muscle and their mechanical properties over a wide range of transmural pressures. Capillaries were fixed at controlled pressures and studied with intravital and electron microscopy. Capillary lumen dimensions depend on the local transmural pressure, with irregular and partially collapsed cross-sections at low transmural pressures and circular cross-sections at elevated pressures. The average circumferential wall stress is a nonlinear function of the circumferential stretch. Elevation of the transcapillary pressure serves to increase the endothelial surface area exposed to the lumen and to the basement membrane while the average endothelial thickness and cell volume decrease. The number of vesicles in the endothelium and their average size decrease with the stretching of the endothelial cell. The balance of membrane area measurements on the vesicles and on the cell surface show that the total membrane surface is conserved at all pressures, and the vesicles become unfolded during stretching of the endothelial cells. This suggests that the vesicle membrane serves as a reservoir for the increase of endothelial surface membrane area during capillary distension. Under normal or elevated capillary pressure, virtually no evidence for pseudopod formation by the endothelial cells was detected. If the capillary transmural pressure was reduced to zero in the presence of autologous plasma for periods of about 10 min, limited evidence for pseudopods in less than 10% of the capillary sections was seen. If the muscle capillaries were perfused with plasmalyte and fixed at low pressures, all capillaries exhibited pseudopod formation. Addition of plasma proteins prevented most pseudopod formations. Endothelial pseudopods are depleted of vesicles and form sheet-like projections. Once pseudopods are formed at low pressure, they cannot readily be unfolded by elevation of the capillary transmural pressure. Pseudopods appear to consist of a crosslinked actin matrix and may have a strong effect on the resistance to blood flow in capillaries. These results may be relevant with respect to capillary blood flow at low pressures.