Miedema H, Assmann S M
Biology Department, The Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA.
J Membr Biol. 1996 Dec;154(3):227-37. doi: 10.1007/s002329900147.
ABA stimulation of outward K+ current (IK,out) in Vicia faba guard cells has been correlated with a rise in cytosolic pH (pHi). However, the underlying mechanism by which IK,out is affected by pHi has remained unknown. Here, we demonstrate that pHi regulates outward K+ current in isolated membrane patches from Vicia faba guard cells. The stimulatory effect of alkalinizing pHi was voltage insensitive and independent of the two free calcium levels tested, 50 nM and 1 microM. The single-channel conductance was only slightly affected by pHi. Based on single-channel measurements, the kinetics of time-activated whole-cell current, and the analysis of current noise in whole-cell recordings, we conclude that alkaline pHi enhances the magnitude of IK,out by increasing the number of channels available for activation. The fact that the pHi effect is seen in excised patches indicates that signal transduction pathways involved in the regulation of IK,out by pHi, and by implication, components of hormonal signal transduction pathways that are downstream of pHi, are membrane-delimited.
蚕豆保卫细胞中脱落酸（ABA）对外向钾离子电流（IK,out）的刺激作用与胞质pH值（pHi）升高相关。然而，pHi影响IK,out的潜在机制仍不清楚。在此，我们证明pHi可调节蚕豆保卫细胞分离膜片中的外向钾离子电流。碱化pHi的刺激作用对电压不敏感，且与所测试的两个游离钙水平（50 nM和1 microM）无关。单通道电导仅受pHi轻微影响。基于单通道测量、时间激活全细胞电流的动力学以及全细胞记录中的电流噪声分析，我们得出结论，碱性pHi通过增加可用于激活的通道数量来增强IK,out的幅度。在切除的膜片中观察到pHi效应这一事实表明，参与pHi对IK,out调节的信号转导途径，以及与之相关的pHi下游激素信号转导途径的组成部分，是由膜界定的。
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