Sekiguchi S, Chujyo N
Jpn J Pharmacol. 1978 Oct;28(5):763-73. doi: 10.1254/jjp.28.763.
The apparent diffusion coefficient of Ca ions in the extracellular space of guinea pig taenia coli was estimated from model experiments to be 3.2 x 10(-6) cm2 sec -1, while the relationship between Ca concentration in the medium and tonic tension in 40 mM K-contracture was measured in the same muscle both in the presence and absence of dextran 10. On the basis of these experiments and certain assumptions, the time course of tension decline by Ca withdrawal during K-contracture was calculated. Under all dextran concentrations tested (0--15%) the calculated time course of tension decline was in good agreement with one actually observed except in a short period of time immediately after Ca withdrawal. The results suggested that Ca distribution in the extracellular space during the loss of Ca is in good agreement with the diffusion theory in cylinder, and that each muscle fiber shows its tension without delay in response to the change in Ca concentration in the vicinity of the fiber according to the tonic tension-Ca relationship mentioned above. The discrepancy between calculation and observation was partially explained on an experimental basis.
通过模型实验估计，豚鼠结肠带细胞外空间中钙离子的表观扩散系数为3.2×10⁻⁶ cm²·s⁻¹，同时在有无右旋糖酐10的情况下，在同一块肌肉中测量了培养基中钙浓度与40 mM钾收缩时强直张力之间的关系。基于这些实验和某些假设，计算了钾收缩期间因钙撤离导致的张力下降的时间进程。在所有测试的右旋糖酐浓度（0 - 15%）下，除了钙撤离后立即的短时间内，计算出的张力下降时间进程与实际观察到的情况非常吻合。结果表明，钙流失期间细胞外空间中的钙分布与圆柱体中的扩散理论高度一致，并且根据上述强直张力 - 钙关系，每个肌纤维在纤维附近钙浓度发生变化时能无延迟地表现出其张力。计算结果与观察结果之间的差异在实验基础上得到了部分解释。
