Stretch-activated (SA) channels were studied in smooth muscle cells isolated from mesenteric resistance arteries using the whole-cell patch-clamp method. Membrane stretch was achieved by cell inflation after application of positive pressure through a patch electrode. 2. In the voltage-clamp configuration, cell inflation increased and cell deflation decreased the membrane conductance. Conductance of the evoked current depended on the increase in cross-sectional area of the cell. The current-voltage relationship was linear between -80 and 0 mV, while further hyperpolarization showed a slight inward rectification. 3. The reversal potential of the SA current depended on the extracellular Na+ concentration, suggesting that the inward SA current was carried predominantly by Na+. The SA current was also carried by other cations, suggesting that the channel responsible for this current is a non-selective cation channel. The permeability sequence of cations as assessed by reversal potential was as follows: K+ > or = CS+ > or = Na+ > Li+. The channel was also permeable to Ca2+. 4. Extracellular Ca2+ and Gd3+ inhibited the SA current carried by monovalent cations in a concentration-dependent manner with IC50 (concentration giving 50% of maximal inhibition) values of 0.9 mM and 14 microM, respectively. 5. In the current-clamp configuration, membrane stretch depolarized the cell, and 100 microM Gd3+ inhibited the stretch-induced depolarization. 6. The results suggest that SA cation channels exist in arterial smooth muscle cells. Activation of the channels may modify membrane potential and intracellular ionic environment, and promote stretch-mediated cell responses.
摘要
使用全细胞膜片钳方法，对从肠系膜阻力动脉分离出的平滑肌细胞中的牵张激活（SA）通道进行了研究。通过膜片电极施加正压后使细胞膨胀来实现膜牵张。2. 在电压钳模式下，细胞膨胀使膜电导增加，细胞收缩使膜电导降低。诱发电流的电导取决于细胞横截面积的增加。电流 - 电压关系在 -80 至 0 mV 之间呈线性，而进一步超极化则显示出轻微的内向整流。3. SA 电流的反转电位取决于细胞外 Na⁺浓度，表明内向 SA 电流主要由 Na⁺携带。SA 电流也由其他阳离子携带，表明负责该电流的通道是一种非选择性阳离子通道。通过反转电位评估的阳离子通透性顺序如下：K⁺≥Cs⁺≥Na⁺＞Li⁺。该通道也对 Ca²⁺通透。4. 细胞外 Ca²⁺和 Gd³⁺以浓度依赖性方式抑制单价阳离子携带的 SA 电流，IC50（产生最大抑制 50%的浓度）值分别为 0.9 mM 和 14 μM。5. 在电流钳模式下，膜牵张使细胞去极化，100 μM Gd³⁺抑制牵张诱导的去极化。6. 结果表明，SA 阳离子通道存在于动脉平滑肌细胞中。通道的激活可能会改变膜电位和细胞内离子环境，并促进牵张介导的细胞反应。
