Kotera T, Brown P D
Department of Physiological Sciences, University of Manchester, UK.
J Membr Biol. 1993 May;134(1):67-74. doi: 10.1007/BF00233476.
We have identified a whole-cell Cl- current activated by hyposmotic stress in rat lacrimal acinar cells using the patch-clamp technique. Superfusion of isolated single cells with hyposmotic solution (80% of control osmolarity) caused a gradual increase of the current, which was reversed on return to the control solution. The current-voltage relationship showed outward rectification, and the current showed time and voltage dependence: slowly activated by depolarizing voltages and rapidly inactivated by hyperpolarizing voltages. The increase in current was not observed when intracellular Ca2+ was chelated with EGTA. It was also inhibited by the absence of extracellular Ca2+, or the presence of gadolinium ions (20 microM Gd3+). We conclude that in rat lacrimal acinar cells hyposmotic stress activates Ca(2+)-dependent Cl- channels as a result of Ca2+ influx through a Gd(3+)-sensitive pathway. The Cl- channels involved appear to be indistinguishable from those activated by muscarinic stimulation. The inhibitory effect of Gd3+ suggests that stretch-activated nonselective cation channels may be responsible for the Ca2+ influx.
我们运用膜片钳技术，在大鼠泪腺腺泡细胞中鉴定出一种由低渗应激激活的全细胞氯离子电流。用低渗溶液（对照渗透压的80%）灌流分离的单个细胞，会使电流逐渐增加，当恢复到对照溶液时电流逆转。电流-电压关系呈外向整流，且电流呈现时间和电压依赖性：被去极化电压缓慢激活，被超极化电压快速失活。当用乙二醇双四乙酸（EGTA）螯合细胞内钙离子时，未观察到电流增加。细胞外无钙离子或存在钆离子（20微摩尔Gd3+）时，电流也受到抑制。我们得出结论，在大鼠泪腺腺泡细胞中，低渗应激通过钆敏感途径使钙离子内流，从而激活钙依赖性氯离子通道。所涉及的氯离子通道似乎与毒蕈碱刺激激活的通道无法区分。钆离子的抑制作用表明，牵张激活的非选择性阳离子通道可能是钙离子内流的原因。
