Effects of ramp shortening during linear phase of relaxation on [Ca2+]i in intact skeletal muscle fibers.
Effects of ramp shortening during linear phase of relaxation on [Ca2+]i in intact skeletal muscle fibers.
复制标题
线性松弛阶段斜坡缩短对完整骨骼肌纤维中 [Ca2]i 的影响。
DOI：
10.1152/ajpcell.1999.276.1.c152
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Julian,FJ
中科院分区：
文献类型：
--
作者：
Jiang,Y;Julian,FJ
研究了Vu处的缩短距离、无载荷缩短速度和细丝重叠对肌肉松弛期间释放的额外Ca 2+量（如隆起面积所示）的影响。使用3°C下的单个完整青蛙骨骼肌纤维。肌浆游离钙浓度（[Ca ~（2+）]i）用fura ~ 2盐注射法测定。在松弛的线性阶段，在具有不同尺寸的完全重叠处或在具有固定尺寸的变化重叠处施加斜坡。在完全重叠时，通过使用凸块面积的一半等于25.9nm的S形曲线拟合凸块面积对斜坡尺寸的图。使用100 nm/半肌节的固定斜坡尺寸，通过在103.5 μm处与SLmax相交的直线拟合凸块面积与平均肌节长度（SLm）的图，接近于无重叠。结果表明，在50 nm/半肌节内完成的过渡连接的横桥的分布从等距的情况下，一个适合卸载缩短atVuis，并支持的观点，即在重叠区连接的横桥影响的Ca 2+的亲和力肌钙蛋白C在细丝。
The effects of shortening distance atVu, the unloaded shortening speed, and filament overlap on the amount of extra Ca2+released during relaxation in muscle, as indicated by the bump area, were studied. Single, intact frog skeletal muscle fibers at 3°C were used. The myoplasmic free Ca2+concentration ([Ca2+]i) was estimated by using fura 2 salt injected into the myoplasm. Ramps were applied, either at full overlap with different sizes or at varying overlaps with a fixed size, in the linear phase of relaxation. At full overlap, a plot of bump area vs. ramp size was fit by using a sigmoidal curve with one-half of the bump area equal to 25.9 nm. With a fixed ramp size of 100 nm/half-sarcomere, the plot of bump area vs. mean sarcomere length (SLm) was fit by a straight line intersecting the SLmaxis at ∼3.5 μm, close to just no overlap. The results suggest that the transition in the distribution of attached cross bridges from the isometric case to one appropriate for unloaded shortening atVuis completed within 50 nm/half-sarcomere and support the view that attached cross bridges in the overlap zone influence the affinity of Ca2+for troponin C in the thin filament.