Thin filament regulation of shortening velocity in rat skinned skeletal muscle: effects of osmotic compression.
Thin filament regulation of shortening velocity in rat skinned skeletal muscle: effects of osmotic compression.
复制标题
大鼠皮骨骼肌缩短速度的细丝调节：渗透压的影响。
DOI：
10.1113/jphysiol.1988.sp017036
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Moss,RL
中科院分区：
文献类型：
--
作者：
Metzger,JM;Moss,RL
1. 在存在或不存在 5% 葡聚糖诱导的渗透压缩的情况下，在不同程度的细丝 Ca2+ 激活下，检查大鼠慢肌比目鱼肌的带皮单纤维的最大缩短速度 (Vmax)。 2. 在最大 Ca2+ 激活水平下，随着缩短程度的变化，Vmax 保持恒定，平均值为 1.43 +/- 0.05 肌肉长度/秒（平均值 + S.E.M.，n = 13）。当通过降低 Ca2+ 浓度来减少细丝激活时，无负荷缩短由初始高速阶段（在 20-80 nm/半肌节范围内缩短）和随后的低速阶段（更大程度的缩短）组成。 3. 在没有葡聚糖的情况下，高速缩短阶段的 Vmax 在较宽的激活范围内相对不变；然而，在非常低的激活水平下，产生的张力小于峰值的 5%。 Vmax 急剧下降。相比之下，用葡聚糖径向压缩的纤维直径与完整纤维的直径相当，当细丝激活在很大范围内变化时，高速阶段的 Vmax 显着降低。这些发现与以下观点一致：带皮纤维的扩展长丝晶格中的跨桥不承受与完整纤维中一样大的轴向压缩力（Goldman & Simmons，1986；Goldman，1987），而是随着纤维缩短而弯曲。 4.随着对照纤维和渗透压缩纤维中细丝激活的减少，缩短低速阶段的 Vmax 值降低。低速阶段仅在细丝激活水平降低时发生，可能是一群缓慢解离的横桥的表现，这些桥随着缩短而变得负应变并反对收缩。
1. Maximum shortening velocity (Vmax) was examined in skinned single fibres from rat slow‐twitch soleus muscles at various degrees of Ca2+ activation of the thin filament, in the presence and absence of osmotic compression induced by 5% dextran. 2. At maximal levels of Ca2+ activation, Vmax remained constant as the extent of shortening was varied, with values averaging 1.43 +/‐ 0.05 muscle lengths/s (mean + S.E.M., n = 13). When thin filament activation was reduced by lowering the concentration of Ca2+, unloaded shortening consisted of an initial high‐velocity phase for extents of shortening in the range 20‐80 nm/half‐sarcomere, and a subsequent low‐velocity phase for greater extents of shortening. 3. In the absence of dextran, Vmax in the high‐velocity phase of shortening was relatively invariant over a wide range of activation; however, at very low levels of activation, yielding tensions less than 5% of the peak value. Vmax declined precipitously. In contrast, fibres compressed radially with dextran to diameters comparable to those of intact fibres demonstrated a marked decrease in Vmax in the high‐velocity phase when thin filament activation was varied over a wide range. These findings are consistent with the idea that cross‐bridges in the expanded filament lattice of skinned fibres do not bear as great an axial compressive force as in intact fibres (Goldman & Simmons, 1986; Goldman, 1987) but instead buckle as the fibre shortens. 4. The value of Vmax in the low‐velocity phase of shortening decreased as thin filament activation was reduced in both control and osmotically compressed fibres. The low‐velocity phase, which occurred only at reduced levels of thin filament activation, may be a manifestation of a population of slowly dissociating crossbridges which with shortening become negatively strained and oppose contraction.