Vega-Saenz de Miera E, Rudy B
Department of Physiology and Biophysics, New York University Medical Center, N.Y. 10016.
Biochem Biophys Res Commun. 1992 Aug 14;186(3):1681-7. doi: 10.1016/s0006-291x(05)81602-x.
External application of hydrogen peroxide (H2O2) was found to inhibit the time-dependent fast inactivation process of three cloned voltage-gated K+ channels expressed in Xenopus oocytes: KShIIIC, KShIIID and HukII. As expected from kinetic models where some channels are still opening while a significant fraction of channels is already inactivated there was a large increase in current magnitude concomitant to inactivation block. The channels otherwise functioned normally. The effects of H2O2 were specific (other cloned voltage-gated K+ channels were not affected), and reversible, the currents returned to normal upon removal of the H2O2. H2O2 is produced during normal metabolism; it could act as a modulator of excitability through effects on K+ channels if effective local concentrations are reached in neuronal regions close to the channel. KShIIIC and KShIIID currents are very similar to an O2-sensitive K+ current present in type I cells of the carotid body which is believed to underlie the modulation of excitability of these cells by changes in arterial O2 pressure. H2O2 has been proposed as an intermediary between O2 and cellular response in the carotid body; our results provide support for this model.
研究发现，在非洲爪蟾卵母细胞中表达的三种克隆电压门控钾通道（KShIIIC、KShIIID和HukII）的时间依赖性快速失活过程可被过氧化氢（H2O2）的外部应用所抑制。从动力学模型可以预期，当一部分通道已经失活而仍有一些通道在开放时，失活阻滞会伴随电流幅度大幅增加。这些通道在其他方面功能正常。H2O2的作用具有特异性（其他克隆的电压门控钾通道不受影响）且是可逆的，去除H2O2后电流恢复正常。H2O2在正常代谢过程中产生；如果在靠近通道的神经元区域达到有效局部浓度，它可能通过对钾通道的作用作为兴奋性的调节剂。KShIIIC和KShIIID电流与颈动脉体I型细胞中存在的一种对氧敏感的钾电流非常相似，据信这种电流是动脉氧分压变化对这些细胞兴奋性调节的基础。H2O2已被提出作为颈动脉体中氧与细胞反应之间的中介物；我们的结果为该模型提供了支持。
