The effect of sarcomere length on triad location in intact feline caudofemoralis muscle fibres
The effect of sarcomere length on triad location in intact feline caudofemoralis muscle fibres
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DOI：
10.1023/a:1005309107903
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发表时间：
1998-06-01
影响因子：
2.7
通讯作者：
Loeb, GE
中科院分区：
文献类型：
--
作者：
Brown, IE;Kim, DH;Loeb, GE
哺乳动物骨骼肌肌节内三联体的位置传统上被定义为“A-I 连接处”。我们试图通过系统地检查肌节内三联体在肌节长度的生理范围内的位置来验证这一说法。这项研究是使用来自尾股肌的完整猫科肌纤维进行的，尾股肌是一种来自后肢的专门的快肌纤维。我们在完整纤维中的结果表明，Z 带和三联体 (ZT) 之间的距离在本研究中检查的肌节长度 (SL) 范围内 (1.8-3.4 μ m) 相对恒定。ZT 和 SL 之间的斜率测量为 0.06 +/- 0.01 (r = 0.36,p < 0.001)，而 M 线到三联体距离 (MT) 和 SL 之间的斜率测量为为 0.44 +/- 0.01（r > 0.9，p < 0.001）。平均 ZT 为 0.52 +/- 0.07 μm，对应于沿着细丝大约一半的三元组位置。这些结果不支持关于三合会位置的传统说法。这些结果也不支持最近使用大鼠趾长伸肌（也是后肢均匀快肌）进行的化学剥皮肌纤维进行的类似研究，其中观察到 ZT 和 SL 之间的斜率为 0.25（r > 0.9，p < 0.01）。然而，这些结果与使用来自快肌大鼠半腱肌的完整纤维的结果在质量上一致。基于已知的形态，我们认为支持三联体位置的唯一结构是 SR 本身，并且 SR 在肌节内的非均匀分布可能是维持细丝中间区域附近三联体位置的原因。我们还认为，将三元组定位在细丝的中间区域可能存在最佳设计原因。 (C) 查普曼霍尔有限公司
The location of triads within a mammalian skeletal muscle sarcomere has traditionally been defined as 'at the A-I junction'. We attempted to verify this statement by examining systematically the location of triads within the sarcomere over the physiological range of sarcomere lengths. This study was conducted using intact feline muscle fibres from caudofemoralis - an exclusively fast-twitch muscle from the hindlimb. Our results in intact fibres indicate that the distance between the Z-band and triad (ZT) is relatively constant over the range of sarcomere lengths (SLs) examined in this study (1.8-3.4 mu m) The slope between ZT and SL was measured to be 0.06 +/- 0.01 (r = 0.36,p < 0.001) while the slope between the M-line to triad distance (MT) and SL was measured to be 0.44 +/- 0.01 (r > 0.9, p < 0.001). The mean ZT was 0.52 +/- 0.07 mu m, which corresponds to a triad location approximately halfway along the thin filaments. These results do not support the traditional statement regarding triad location. Nor do these results support a similar recent study conducted using chemically skinned muscle fibres from rat extensor digitorum longus (also a homogeneously fast-twitch muscle of the hindlimb), in which a slope of 0.25 was observed between ZT and SL (r > 0.9,p < 0.01). These results are, however, in qualitative agreement with results using intact fibres from fast-twitch rat semitendinosus. Based upon known morphology, we suggest that the only structure supporting triad position is the SR itself, and that a non-homogeneous distribution of the SR within the sarcomere might be responsible for maintaining triad location near the mid-region of the thin filaments. We also suggest that there might be optimal design reasons for locating the triads at the mid-region of the thin filaments. (C) Chapman & Hall Ltd.