藤壶肌纤维的肌浆固定电荷与游离钙离子浓度。

The myoplasmic fixed charges of the barnacle muscle fiber and the free Ca2+ concentration.

作者信息

Caillé J P

出版信息

Biochim Biophys Acta. 1981 Apr 3;673(4):416-24. doi: 10.1016/0304-4165(81)90473-6.

Abstract

An experimental model was recently developed to measure the myoplasm density of fixed charges (Caillé J.P. (1979) Biochim. Biophys. Acta 585, 300-313). The effect of ATP, Mg2+ and Ca2+ suggests that the myoplasmic thermodynamically effective charge density (phi X) decreases during muscular contraction. In order to determine if this reduction was due to either ATP, Mg2+ or Ca2+, the phi X dependence on those substances was studied. The results indicated that the addition of MgCl2 (2 mM) reduced phi X by 10 to 30% depending on the water content of the myoplasm. A reduction of phi X was also observed with the addition of (10(-4) M) Ca2+, but the presence of ATP was necessary for this reduction to occur. Finally when EGTA was added to the external solution in order to control the level of free Ca2+, an important reduction of phi X (40%) was observed for a pCa equal to 5.7 (water content 76.1 +/- 0.3 ml/100 g). These results allowed a correlation between the reduction of the myoplasmic fixed charges and the turning on of the contractile machinery.

摘要

最近开发了一种实验模型来测量固定电荷的肌浆密度（Caillé J.P.（1979年）《生物化学与生物物理学报》585卷，300 - 313页）。ATP、Mg²⁺和Ca²⁺的作用表明，在肌肉收缩过程中肌浆的热力学有效电荷密度（φX）会降低。为了确定这种降低是由于ATP、Mg²⁺还是Ca²⁺引起的，研究了φX对这些物质的依赖性。结果表明，添加MgCl₂（2 mM）会使φX降低10%至30%，具体取决于肌浆的含水量。添加（10⁻⁴ M）Ca²⁺时也观察到φX降低，但这种降低需要ATP的存在。最后，当向外部溶液中添加乙二醇双（2-氨基乙基醚）四乙酸（EGTA）以控制游离Ca²⁺水平时，对于pCa等于5.7（含水量76.1±0.3 ml/100 g），观察到φX显著降低（40%）。这些结果使得肌浆固定电荷的降低与收缩机制的启动之间建立了关联。