Estimates of force generation or shortening obtained from smooth muscle tissues are valid for individual cells only if each cell is contracting homogeneously and if cells anatomically arranged in series are mechanically coupled. These two assumptions were tested and shown to be valid for the pig carotid media under certain conditions. Homogeneity of cellular responses in carotid strips was estimated from the motion of markers on the tissue during K+ -induced isometric contractions. When tissues were stretched to L0 (the optimum length for force generation), there was little marker movement on stimulation. However, considerable marker movement was observed on stimulation at shorter muscle lengths, reflecting localized shortening or stretching. The mechanical coupling of the very small cells in the media was determined by measuring the dependence of cell length on tissue length. Tissues were fixed with glutaraldehyde during isometric contractions at various tissue lengths (0.4--1.1 x L0). The fixed tissues were macerated with acid and the lengths of the dispersed cells were measured. Cell lengths were broadly distributed at all muscle lengths. However, the direct proportionality between mean cell length and muscle length (as a fraction of L0) indicated that cells which are anatomically in series are coupled force-transmitting structures. We conclude that valid estimates of cellular mechanical function in this preparation can be obtained from tissue measurements at lengths greater than about 0.9L0.
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机译：仅当每个细胞均质收缩并且解剖上串联排列的细胞机械耦合时，才能从平滑肌组织获得的力产生或缩短的估计值对单个细胞有效。对这两个假设进行了测试，并证明它们在某些条件下对猪颈动脉中的介质有效。根据K +诱导的等轴测收缩过程中组织上标志物的运动，估算颈动脉条中细胞反应的同质性。当组织被拉伸到L0（最合适的力产生长度）时，刺激时标记物移动很少。然而，在较短的肌肉长度处刺激时观察到相当大的标记运动，反映了局部的缩短或拉伸。通过测量细胞长度对组织长度的依赖性来确定培养基中非常小的细胞的机械偶联。在各种组织长度（0.4--1.1 x L0）的等距收缩过程中，用戊二醛固定组织。用酸浸软固定的组织，并测量分散的细胞的长度。细胞长度广泛分布于所有肌肉长度。但是，平均细胞长度和肌肉长度（作为L0的一部分）之间的直接比例关系表明，在解剖学上串联的细胞是耦合的力传递结构。我们得出的结论是，可以从组织测量值大于约0.9L0的长度中获得对这种制剂中细胞机械功能的有效估计。
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