Chan C K, Durieux M E
University of Virginia, Charlottesville, USA.
Anesthesiology. 1997 Mar;86(3):660-9. doi: 10.1097/00000542-199703000-00019.
Volatile anesthetics have been found to interfere with the functioning of several G protein-coupled receptors, effects that may be relevant to the mechanism of anesthetic action. Lysophosphatidate (1-acyl-2-sn-glycero-3-phosphate; LP) is the simplest natural phospholipid. It has pronounced biological effects and signals through a specific G protein-coupled receptor. Because of its lipophilicity, the LP receptor is a feasible site of anesthetic interaction. Therefore, the authors investigated the effects of halothane and isoflurane on LP signaling using Xenopus oocytes.
Mature oocytes were harvested from Xenopus frogs, isolated, and defolliculated manually. Lysophosphatidate receptors are endogenously present in these cells. Angiotensin receptors were expressed recombinantly to study anesthetic effects on intracellular signaling. Oocytes were studied individually with a two-electrode voltage clamp at room temperature. Integrated Ca(2+)-activated Cl- currents (ICl(Ca)) were used to evaluate the effects of anesthetics on changes in intracellular Ca2+ concentration in response to receptor agonists (10(-7) M LP or 10(-7) M angiotensin II) or intracellular inositoltrisphosphate (IP3) injection.
Halothane depressed LP signaling in a concentration-dependent manner, with half-maximal inhibition at 0.23 mM and virtually complete inhibition at 0.34 mM. Responses could be recovered after an anesthetic-free wash. Oocyte injection with heparin, an IP3 receptor antagonist, completely blocked LP and angiotensin signaling, indicating similar IP3- dependent pathways. However, ICl(Ca) induced by angiotensin receptor activation or intracellular IP3 injection were not inhibited by halothane. Isoflurane, at comparable concentrations, did not depress LP responses in oocytes significantly.
Lipid-mediator signaling can be affected profoundly by volatile anesthetics. At clinically relevant concentrations, halothane and isoflurane have different effects on LP signaling. The inhibitory effects of halothane on the LP signaling pathway occur before the IP3 receptor.
已发现挥发性麻醉剂会干扰多种G蛋白偶联受体的功能，这些作用可能与麻醉作用机制相关。溶血磷脂酸（1-酰基-2- sn -甘油-3-磷酸；LP）是最简单的天然磷脂。它具有显著的生物学效应，并通过特定的G蛋白偶联受体进行信号传导。由于其亲脂性，LP受体是麻醉相互作用的一个可行位点。因此，作者利用非洲爪蟾卵母细胞研究了氟烷和异氟烷对LP信号传导的影响。
从非洲爪蟾采集成熟卵母细胞，分离并手动去除卵泡。这些细胞内源性存在溶血磷脂酸受体。重组表达血管紧张素受体以研究麻醉剂对细胞内信号传导的影响。在室温下用双电极电压钳对卵母细胞进行单独研究。整合的钙激活氯电流（ICl(Ca)）用于评估麻醉剂对受体激动剂（10(-7) M LP或10(-7) M血管紧张素II）或细胞内注射肌醇三磷酸（IP3）后细胞内钙离子浓度变化的影响。
氟烷以浓度依赖性方式抑制LP信号传导，在0.23 mM时半数最大抑制，在0.34 mM时几乎完全抑制。在无麻醉剂冲洗后反应可恢复。用IP3受体拮抗剂肝素注射卵母细胞可完全阻断LP和血管紧张素信号传导，表明存在相似的IP3依赖性途径。然而，血管紧张素受体激活或细胞内注射IP3诱导的ICl(Ca)不受氟烷抑制。在相当浓度下，异氟烷对卵母细胞中的LP反应无显著抑制作用。
挥发性麻醉剂可深刻影响脂质介质信号传导。在临床相关浓度下，氟烷和异氟烷对LP信号传导有不同影响。氟烷对LP信号传导途径的抑制作用发生在IP3受体之前。
