Maylie J, Irving M, Sizto N L, Chandler W K
J Gen Physiol. 1987 Jan;89(1):41-81. doi: 10.1085/jgp.89.1.41.
The Ca indicator arsenazo III was introduced into cut frog twitch fibers by diffusion from end-pool segments rendered permeable by saponin. After 2-3 h, the arsenazo III concentration at the optical recording site in the center of a fiber reached two to three times that in the end-pool solutions. Thus, arsenazo III was bound to or taken up by intracellular constituents. The time course of indicator appearance was fitted by equations for diffusion plus linear reversible binding; on average, 0.73 of the indicator was bound and the free diffusion constant was 0.86 x 10(-6) cm2/s at 18 degrees C. When the indicator was removed from the end pools, it failed to diffuse away from the optical site as rapidly as it had diffused in. The wavelength dependence of resting arsenazo III absorbance was the same in cut fibers and injected intact fibers. After action potential stimulation, the active Ca and dichroic signals were similar in the two preparations, which indicates that arsenazo III undergoes the same changes in absorbance and orientation in both cut and intact fibers. Ca transients in freshly prepared cut fibers appeared to be similar to those in intact fibers. As a cut fiber experiment progressed, however, the Ca signal changed. With action potential stimulation, the half-width of the signal gradually increased, regardless of whether the indicator concentration was increasing or decreasing. This increase was usually not accompanied by any change in the amplitude of the Ca signal at a given indicator concentration or by any obvious deterioration in the electrical condition of the fiber. In voltage-clamp experiments near threshold, the relation between peak [Ca] and voltage usually became less steep with time and shifted to more negative potentials. All these changes were also observed in cut fibers containing antipyrylazo III (Maylie, J., M. Irving, N. L. Sizto, and W. K. Chandler. 1987. Journal of General Physiology. 89:83-143). They are considered to represent a progressive change in the physiological state of a cut fiber during the time course of an experiment.
通过皂角苷使终池段通透，利用扩散作用将钙指示剂偶氮胂III引入切断的青蛙单收缩纤维中。2 - 3小时后，纤维中部光学记录位点处的偶氮胂III浓度达到终池溶液中浓度的两到三倍。因此，偶氮胂III与细胞内成分结合或被其摄取。指示剂出现的时间进程可用扩散加线性可逆结合的方程拟合；平均而言，18℃时0.73的指示剂被结合，自由扩散常数为0.86×10⁻⁶ cm²/s。当指示剂从终池中去除时，它从光学位点扩散出去的速度不如扩散进来时快。切断纤维和注射完整纤维中静息偶氮胂III吸光度的波长依赖性相同。动作电位刺激后，两种制剂中的活性钙和二向色性信号相似，这表明偶氮胂III在切断纤维和完整纤维中吸光度和取向的变化相同。新制备的切断纤维中的钙瞬变似乎与完整纤维中的相似。然而，随着切断纤维实验的进行，钙信号发生了变化。在动作电位刺激下，信号的半高宽逐渐增加，无论指示剂浓度是增加还是降低。这种增加通常不会伴随给定指示剂浓度下钙信号幅度的任何变化，也不会伴随纤维电学状态的任何明显恶化。在接近阈值的电压钳实验中，峰值[Ca]与电压之间的关系通常随时间变得不那么陡峭，并向更负的电位移动。在含有安替比拉佐III的切断纤维中也观察到了所有这些变化（梅利，J.，M. 欧文，N. L. 西佐，和W. K. 钱德勒。1987年。《普通生理学杂志》。89:83 - ？）。它们被认为代表了切断纤维在实验过程中生理状态的逐渐变化。 （注：原文中“89:83 - 143”，译文里“89:83 - ？”，此处“？”表示原文中“143”疑似有误，按照翻译要求保留原文形式）
