非洲爪蟾卵母细胞中对钙、电压和渗透压应激敏感的电流及其与单个机械门控通道的关系。

Calcium-, voltage- and osmotic stress-sensitive currents in Xenopus oocytes and their relationship to single mechanically gated channels.

Zhang Y, Hamill O P

Physiology and Biophysics, University of Texas Medical Branch, Galveston, TX 77555-0641, USA.

J Physiol. 2000 Feb 15;523 Pt 1(Pt 1):83-99. doi: 10.1111/j.1469-7793.2000.t01-2-00083.x.

Abstract

Patch recordings from Xenopus oocytes indicated that mechanically gated (MG) channels are expressed at a uniform surface density ( approximately 1 channel microm-2) with an estimated > 3 x 106 MG channels per oocyte that could generate microamps of current at +/-50 mV. 2. Removal of external Ca2+ induced a membrane conductance that differed from MG channels in ion selectivity, pharmacology and sensitivity to connexion-38. 3. Depolarization to +50 mV activated a Na+-selective, a Cl--selective and a non-selective conductance. Hyperpolarization to -150 mV activated a non-selective conductance. None of these conductances appeared to be mediated by MG channels. 4. Hypotonicity (25 %) failed to evoke any change in membrane conductance in the majority of defolliculated oocytes. Hypertonicity (200 %) evoked a large non-selective (PK /PCl approximately 1) membrane conductance that was not blocked by 100 microM Gd3+. 5. Although the above stimuli could activate a variety of whole-oocyte conductances, including three novel conductances, they did not involve MG channel activation. Possible mechanisms underlying the discrepancy between observed conductances and those anticipated from patch-clamp studies are discussed.

摘要

非洲爪蟾卵母细胞的膜片钳记录表明，机械门控（MG）通道以均匀的表面密度（约1个通道/μm²）表达，每个卵母细胞估计有超过3×10⁶个MG通道，在±50 mV时可产生微安级电流。2. 去除细胞外Ca²⁺会诱导一种膜电导，其在离子选择性、药理学及对连接蛋白38的敏感性方面与MG通道不同。3. 去极化至+50 mV会激活一种Na⁺选择性、一种Cl⁻选择性和一种非选择性电导。超极化至 -150 mV会激活一种非选择性电导。这些电导似乎均不由MG通道介导。4. 在大多数去滤泡卵母细胞中，低渗（25%）未能引起膜电导的任何变化。高渗（200%）会诱发一种大的非选择性（PK/PCl约为1）膜电导，该电导不被100 μM Gd³⁺阻断。5. 尽管上述刺激可激活多种全细胞电导，包括三种新的电导，但它们并不涉及MG通道的激活。文中讨论了观察到的电导与膜片钳研究预期的电导之间差异的潜在机制。