The relationship between tension and slowly varying intracellular calcium concentration in intact frog skeletal muscle.
The relationship between tension and slowly varying intracellular calcium concentration in intact frog skeletal muscle.
复制标题
完整青蛙骨骼肌中张力与缓慢变化的细胞内钙浓度之间的关系。
DOI：
10.1113/jphysiol.1997.sp022008
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Julian,FJ
中科院分区：
文献类型：
--
作者：
Morgan,DL;Claflin,DR;Julian,FJ
1. 在青蛙的完整单肌纤维中研究了细胞内钙浓度 [Ca2+]i 和固定端张力之间的关系。环吡嗪酸（CPA）是一种肌浆网 Ca2+ 摄取泵抑制剂，可缓慢降低张力。荧光染料fura-2和furaptra (mag-fura-2)用于估计[Ca2+]i。 2. 在从几秒到超过 100 秒的大范围张力衰减时间内，曲线的陡度和位置都没有一致变化。对于这些接近稳态的曲线，平均以 0.07 pCa 单位发生 10-90% 的张力变化，对应的 Hill 系数 > 25，比之前报道的陡峭得多。可能的伪影可能会将其降低至 15。 3. 甲氧基维拉帕米 (D600) 会减少响应动作电位而释放的钙。 D600 和 CPA 的收缩具有由许多小步骤组成的缓慢上升和缓慢下降。比较上升和下降表明张力-[Ca2+]i 关系几乎没有滞后。 4. 涉及 Ca2+ 和肌球蛋白与细丝结合之间协同作用的模型被证明可以产生张力 -pCa 关系，该关系会因肌球蛋白跨桥分离的平均速率常数而发生显着改变，而肌球蛋白跨桥分离的平均速率常数可能会受到肌节运动的影响。 5. 这种模型被证明能够重现先前报道的完整纤维固定端松弛后期 [Ca2+]i 的小幅上升。
1. The relationship between intracellular calcium concentration, [Ca2+]i, and fixed‐end tension was investigated in intact single muscle fibres from frogs. A slow decline of tension was produced by cyclopiazonic acid (CPA), a sarcoplasmic reticulum Ca2+ uptake pump inhibitor. The fluorescent dyes fura‐2 and furaptra (mag‐fura‐2) were used to estimate [Ca2+]i. 2. Neither the steepness nor the position of the curve changed consistently over a wide range of tension decay times from a few seconds to over 100 s. For these near‐steady‐state curves, the 10‐90% tension change occurred, on average, in 0.07 pCa units, corresponding to a Hill coefficient > 25, much steeper than previously reported. Possible artifacts could reduce that to 15. 3. Methoxyverapamil (D600) reduces the calcium released in response to an action potential. Contractions with D600 and CPA had a slow rise composed of many small steps, and a slow fall. Comparing rise and fall showed little or no hysteresis in the tension‐[Ca2+]i relationship. 4. A model involving co‐operativity between the binding of Ca2+ and myosin to thin filaments is shown to produce a tension‐pCa relationship that is substantially altered by the mean rate constant for detachment of myosin cross‐bridges, which in turn is likely to be affected by sarcomere movements. 5. Such a model is shown to be capable of reproducing the small rise in [Ca2+]i previously reported during the late phase of fixed‐end relaxation of intact fibres.