Goldstein M A, Michael L H, Schroeter J P, Sass R L
Department of Medicine, Baylor College of Medicine, Houston 77030.
Am J Physiol. 1989 Feb;256(2 Pt 2):H552-9. doi: 10.1152/ajpheart.1989.256.2.H552.
We have compared the form and dimensions of the Z-band lattice in rat papillary muscle fixed at rest with and without ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) using electron microscopy and optical diffraction. In unstimulated muscle, the Z-band lattice form called basket weave predominated, and the Z-spacing (defined as the repeat distance of a tetragonal array of cross-cut thin filaments from the same sarcomere) was 23.93 +/- 0.37 nm. Muscles exposed to EGTA exhibited the small square-lattice form, and the Z-spacing was 20.50 +/- 0.19 nm. The Z-spacings in the two lattice forms were similar in cardiac and skeletal muscles such that the decrease in Z-spacing in the transition from basket weave to small square in this study was similar to the increase in Z-spacing previously demonstrated in skeletal muscle in the transition from small square to basket weave. The Z-lattice form and dimensions in unstimulated cardiac muscle resembled those in tetanized skeletal muscle. These findings are consistent with the higher resting tension in cardiac muscle and suggest that Ca2+ may be important for the maintenance of the expanded Z-lattice form.
我们使用电子显微镜和光学衍射技术，比较了在有无乙二醇双（β-氨基乙醚）-N，N，N'，N'-四乙酸（EGTA）的情况下，静止固定的大鼠乳头肌中Z带晶格的形态和尺寸。在未受刺激的肌肉中，称为篮状编织的Z带晶格形态占主导，Z间距（定义为来自同一肌节的横切细肌丝四方阵列的重复距离）为23.93±0.37nm。暴露于EGTA的肌肉呈现小方格晶格形态，Z间距为20.50±0.19nm。两种晶格形态中的Z间距在心肌和骨骼肌中相似，因此在本研究中从篮状编织过渡到小方格时Z间距的减小类似于先前在骨骼肌中从小方格过渡到篮状编织时Z间距的增加。未受刺激的心肌中的Z晶格形态和尺寸类似于强直收缩的骨骼肌中的形态和尺寸。这些发现与心肌中较高的静息张力一致，并表明Ca2+可能对维持扩展的Z晶格形态很重要。
