Kinetics of tension development in skinned cardiac myocytes measured by photorelease of Ca2+.
Kinetics of tension development in skinned cardiac myocytes measured by photorelease of Ca2+.
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通过 Ca2 的光释放测量带皮心肌细胞张力发展的动力学。
DOI：
10.1152/ajpheart.1994.267.5.h1643
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Walker,JW
中科院分区：
文献类型：
--
作者：
Araujo,A;Walker,JW
观察游离钙离子对大鼠心肌细胞张力发育的激活作用。用光敏的钙离子螯合剂NITR-7进行脉冲光解，使肌丝附近的钙离子迅速升高。张力呈指数增加，其一级速率常数(Kca)依赖于钙激活水平。Kca从20%最大Ca(2+)激活张力(Po)时的0.9/-0.2 S-1近似线性增加到85%Po时的4.0/-0.9 S-1，即激活后Kca增加了4倍。将游离镁离子从1 mM减少到0.1 mM，在所有的钙离子水平下，KCA都会加速约两倍。脱皮兔腰大肌纤维的张力发展动力学明显不同：Kca从15%Po时的1.2+/-0.2 S~(-1)非线性增加到85%Po时的最大值17.5+/-1.3 S~(-1)，即激活后Kca增加15倍。此外，降低游离镁离子仅在次峰值钙离子时增加腰大肌纤维的Kca。从腰大肌纤维中提取肌钙蛋白C(TNC)，并与牛心TNC重组，并未显著改变这些张力发展动力学特征。我们得出结论，就钙离子和镁离子对收缩动力学的影响而言，心肌和快速收缩骨骼肌之间存在显著差异，这些差异不能完全归因于TNC亚型的不同。
The rate of activation of tension development by free Ca2+ was examined in skinned rat ventricular myocytes. Pulse photolysis of the photosensitive Ca2+ chelator, Nitr-7, was used to rapidly elevate Ca2+ in the vicinity of the myofilaments. Tension increased exponentially with a first-order rate constant (kCa) that depended on the level of Ca2+ activation. kCa increased approximately linearly from 0.9 +/- 0.2 s-1 at 20% maximal Ca(2+)-activated tension (Po) to 4.0 +/- 0.9 s-1 at 85% Po, representing a fourfold increase in kCa with activation. Reducing free Mg2+ from 1 to 0.1 mM accelerated kCa by about twofold at all levels of Ca2+. Tension development kinetics were significantly different in skinned rabbit psoas fibers: kCa increased nonlinearly from 1.2 +/- 0.2 s-1 at 15% Po to a maximum of 17.5 +/- 1.3 s-1 at 85% Po, representing a 15-fold increase in kCa with activation. Moreover, lowering free Mg2+ increased kCa only at submaximal Ca2+ in psoas fibers. Extraction of troponin C (TNC) from psoas fibers and recombination with bovine cardiac TNC did not significantly alter any of these characteristics of tension development kinetics. We conclude that significant differences exist between cardiac and fast-twitch skeletal muscles in terms of the effects of Ca2+ and Mg2+ on contraction kinetics and that these differences cannot be attributed solely to differences in TNC isoforms.