Tanaka Katsuya, Kawano Takashi, Nakamura Akiyo, Nazari Hossein, Kawahito Shinji, Oshita Shuzo, Takahashi Akira, Nakaya Yutaka
Department of Anesthesiology, Tokushima University School of Medicine, Kuramoto, Tokushima, Japan.
Anesthesiology. 2007 May;106(5):984-91. doi: 10.1097/01.anes.0000265158.47556.73.
Recent evidence indicates that vascular adenosine triphosphate-sensitive potassium (K(ATP)) channels in vascular smooth muscle cells are critical in the regulation of vascular tonus under both physiologic and pathophysiologic conditions. Studies of the interaction of volatile anesthetics with vascular K(ATP) channels have been limited. In the current study, the authors investigated the molecular mechanism of isoflurane's action on vascular K(ATP) channels.
Electrophysiologic experiments were performed using cell-attached and inside-out patch clamp techniques to monitor native vascular K(ATP) channels, and recombinant K(ATP) channels comprised of inwardly rectifying potassium channel subunits (Kir6.1) and the sulfonylurea receptor (SUR2B). Isometric tension experiments were performed in rat thoracic aortic rings without endothelium.
Application of isoflurane (0.5 mM) to the bath solution during cell-attached recordings induced a significant increase in K(ATP) channel activity, which was greatly reduced by pretreatment with a selective inhibitor of protein kinase A (PKA), Rp-cAMPS (100 microM). In inside-out patches, isoflurane did not activate K(ATP) channels. Isoflurane significantly activated wild-type recombinant SUR2B/Kir6.1 in cell-attached patches. Isoflurane-induced activation of wild-type channels was diminished in the PKA-insensitive mutant SUR2B-T633A/Kir6.1, SUR2B-S1465A/Kir6.1, and SUR2B/Kir6.1-S385A. In addition, the authors demonstrated that isoflurane-induced PKA activation was associated with isoflurane-induced decreases in isometric tension in the rat aorta.
These results indicate that isoflurane activates K(ATP) channels via PKA activation. PKA-dependent vasodilation induced by isoflurane also was observed in isometric tension experiments. Analysis of expressed vascular-type K(ATP) channels suggested that PKA-mediated phosphorylation of both Kir6.1 and SUR2B subunits plays a pivotal role in isoflurane-induced vascular K(ATP) channel activation.
最近的证据表明，血管平滑肌细胞中的血管三磷酸腺苷敏感性钾（K(ATP)）通道在生理和病理生理条件下对血管张力的调节中起关键作用。关于挥发性麻醉剂与血管K(ATP)通道相互作用的研究有限。在本研究中，作者研究了异氟烷对血管K(ATP)通道作用的分子机制。
使用细胞贴附式和内面向外膜片钳技术进行电生理实验，以监测天然血管K(ATP)通道以及由内向整流钾通道亚基（Kir6.1）和磺脲类受体（SUR2B）组成的重组K(ATP)通道。在无内皮的大鼠胸主动脉环中进行等长张力实验。
在细胞贴附式记录期间，向浴液中加入异氟烷（0.5 mM）可诱导K(ATP)通道活性显著增加，而用蛋白激酶A（PKA）的选择性抑制剂Rp-cAMPS（100 microM）预处理可大大降低该活性。在内面向外膜片中，异氟烷未激活K(ATP)通道。异氟烷在细胞贴附式膜片中显著激活野生型重组SUR2B/Kir6.1。在对PKA不敏感的突变体SUR2B-T633A/Kir6.1、SUR2B-S1465A/Kir6.1和SUR2B/Kir6.1-S385A中，异氟烷诱导的野生型通道激活减弱。此外，作者证明异氟烷诱导的PKA激活与异氟烷诱导的大鼠主动脉等长张力降低有关。
这些结果表明，异氟烷通过激活PKA来激活K(ATP)通道。在等长张力实验中也观察到异氟烷诱导的PKA依赖性血管舒张。对表达的血管型K(ATP)通道的分析表明，PKA介导的Kir6.1和SUR2B亚基的磷酸化在异氟烷诱导的血管K(ATP)通道激活中起关键作用。
