Iwatsuki N, Nishiyama A
Pflugers Arch. 1982 Apr;393(2):123-9. doi: 10.1007/BF00582933.
The effect of microionophoretic application of isoprenaline on membrane potential and resistance of mouse parotid acinar cells was investigated. For measurements of membrane resistance and the isoprenaline equilibrium potential (Eiso), two microelectrodes were inserted into neighbouring communicating cells. Passing direct current through one of these electrodes, the resting potential could be set at desired levels and Eiso was determined by plotting the relation between the size of the isoprenaline-evoked potential change and the resting potential. Simple depolarizations were found at relatively high resting potentials, while biphasic potential changes in response to isoprenaline (hyperpolarization followed by depolarization) were observed at low resting potentials. Both depolarizing and hyperpolarizing responses to isoprenaline were accompanied by a reduction of membrane resistance. The isoprenaline equilibrium potential in the initial phase of the response was about -53 mV, but had a value of about -24mV in the delayed phase. The initial isoprenaline-evoked potential change was sensitive to alterations in extracellular Na, K and Cl concentrations. The delayed depolarizing response to isoprenaline was markedly reduced by replacing extracellular Na by Tris or extracellular Cl by SO4. These results indicate that isoprenaline opens up conductance pathways permeable to Na and K.
研究了微量离子电泳施加异丙肾上腺素对小鼠腮腺腺泡细胞膜电位和电阻的影响。为了测量膜电阻和异丙肾上腺素平衡电位（Eiso），将两个微电极插入相邻的连通细胞中。通过其中一个电极通入直流电，可以将静息电位设定在所需水平，并通过绘制异丙肾上腺素诱发的电位变化大小与静息电位之间的关系来确定Eiso。在相对较高的静息电位下发现简单的去极化，而在低静息电位下观察到对异丙肾上腺素的双相电位变化（超极化后去极化）。对异丙肾上腺素的去极化和超极化反应均伴有膜电阻降低。反应初始阶段的异丙肾上腺素平衡电位约为 -53 mV，但在延迟阶段的值约为 -24 mV。最初的异丙肾上腺素诱发的电位变化对细胞外Na、K和Cl浓度的改变敏感。用Tris替代细胞外Na或用SO4替代细胞外Cl可明显降低对异丙肾上腺素的延迟去极化反应。这些结果表明，异丙肾上腺素打开了对Na和K通透的电导途径。
