Effects of inhalation anesthesia on hepatic metabolism, Kupffer cell activation and stress protein induction during ischemia-reperfusion

虽然术中肝脏的缺血/缺氧-再灌注/复氧通常发生在全身麻醉下，但由于这种现象，对挥发性麻醉剂对肝脏损伤的直接影响知之甚少。为研究挥发性麻醉药对大鼠肝脏缺血/缺氧再灌注损伤的影响，采用离体肝脏灌流的方法，从禁食24小时的雄性SD大鼠分离肝脏，经门静脉注入改良的Krebs-Ringer碳酸氢盐溶液，在循环灌流充气系统中灌流。将基底液灌流压从1.2降至0.2kPa后再灌流至基线水平，造成缺血。低氧灌流是通过将混合气体中的氧浓度从95%降至10%，然后在95%氧气中复氧产生的。通过肝脏乳酸脱氢酶(LDH)的释放来评估肝脏的活力。测定挥发性麻醉药对SU-…细胞外生成的影响在有或没有超氧化物歧化酶的情况下，测量肝脏中更多的过氧化氢，铁细胞色素c的减少。缺血是明显的，因为向肝脏输送的氧气减少，并导致乳酸产量的增加。再灌流引起乳酸摄取的一过性增加和乳酸脱氢酶释放的显著增加。氟烷、异氟烷和七氟烷可显著减少再灌流期间LDH的释放。异氟醚主要在再灌注期给药对乳酸脱氢酶的释放有明显的抑制作用，而异氟醚主要在缺血期给药对乳酸脱氢酶释放的抑制作用不明显。这些结果表明，挥发性麻醉剂可能通过作用于再灌注期保护空腹肝脏免受早期、非中性粒细胞依赖的缺血再灌注损伤。LDH的释放在复氧后短暂但显著增加，并可被1和2个最低乙醇浓度的异氟醚显著减弱。用氯化Gd抑制Kupffer细胞也能减弱LDH的释放。异氟醚可显著减少再灌流时超氧化物的生成。这些结果表明，异氟醚对肝脏的早期复氧损伤具有保护作用，可能是通过库普弗细胞介导的。异氟醚抑制损伤的机制可能与抑制复氧过程中细胞外超氧化物的生成有关。灌流过程中测定肝脏耗氧量和肝组织丙氨酸氨基转移酶漏出量。用Northernblotting分析肝脏主要应激蛋白热休克蛋白70的基因表达。热休克蛋白70mRNA的表达随再灌流时间的延长而增强。分级缺血或缺氧后的表达水平与计算的肝氧分压显著相关(r^2=0.737，p&lt；0.001，n=21)。这些结果表明，热休克蛋白70mRNA的积聚反映了缺血-再灌注和缺氧-复氧损伤的严重程度，再灌注时的应激反应可以在没有形成血液成分的情况下被触发。细胞内钙稳态的改变参与了缺血-再灌注损伤。在禁食大鼠离体肝灌流模型上，观察了挥发性麻醉药对钙离子载体A23187引起的血流动力学和代谢改变的影响。氟烷、异氟烷和七氟烷维持基础肝脏流量，减少氧气消耗，并短暂增加乳酸净产量。所有麻醉剂均显著减轻A23187给药后肝脏流量和氧耗量的下降。挥发性麻醉药可减轻细胞内钙超载所致的肝血管收缩和氧债。较少

Although intraoperative ischemia/hypoxia-reperfusion/reoxygenation of the liver generally occurs under general anesthesia, little is known about the direct effect of volatile anesthetic agents on hepatic injury due to this phenomenon. The effect of volatile anesthetics on ischemia/hypoxia-reperfusion injury was studied using isolated liver perfusion.The liver was isolated from 24h-fasted, male Sprague-Dawley rats and perfused through the portal vein with a modified Krebs-Ringer bicarbonate solution in a recirculating perfusion-aeration system. Ischemia was induced by reducing the bascline perfusion pressure from 1.2 to 0.2 kPa followed by reperfusion to baseline level. Hypoxic perfusion was produced by decreasing the oxygen concentration in the gas mixture from 95% to 10% followed by reoxygenation at 95% oxygen. Viability of the liver was assessed by lactate dehydrogenase (LDH) release from the liver. To determine the effect of volatile anesthetics on the extracellular generation of su … More peroxide in the liver, the reduction of ferricytochrome c with or without superoxide dismutase was measured.Ischemia was evident by reduced oxygen delivery to the liver, and caused an increase in lactate production. Reperfusion caused a transient increase in lactate uptake and a significant increase in LDH release. Halothane, isoflurane and sevoflurane significantly attenuated LDH release during reperfusion. The suppression of LDH release was evident even when isoflurane was administered mainly during reperfusion period, but not when it was administered mainly during ischemia. These results indicate that volatile anesthetics may protect the fasted liver from carly, neutrophil-independent, ischemia reperfusion injury by acting during the reperfusion phase.LDH release was transiently but dramatically increased by reoxygenation and significantly attenuated by 1 and 2 minimum alvcolar concentrations of isoflurane. Suppression of Kupffer cells with gadolinium chloride also attenuated the LDH release. Isoflurane significantly reduced the superoxide generation on reperfusion. These results show that isoflurane protected the liver from early reoxygenation injury presumably mediated by Kupffer cells. The mechanisms of the inhibitory effect of isoflurane on the injury may involve suppression of extracellular superoxide generation during reoxygenation.Isolated rat livers with cell free perfusion were exposed to various periods of ischemia-reperfusion or hypoxia-reoxygenation. Hepatic oxygen consumption and alanine aminotransferase leakage from liver were determined during perfusion. The gene expression of heat shock protein 70, a major stress protein, of the liver was analyzed by Nothern blotting after perfusion. The expression of heat shock protein 70 mRNA augmented as the reperfusion period increased. The expression level after graded ischemia or hypoxia significantly correlated with the calculated hepatic oxygen bebt (r^2=0.737, p<0.001, n=21). These results suggest that accumulation of heat shock protein 70 mRNA reflects the severity of ischemia-reperfuion and hypoxia-reoxygenation injuries, and that stress response in reperfusion can be triggered without formed elements of blood.Altcrations in intracellular calcium homeostasis have been implicated in ischemia-reperfusion injuries. The effects of volatile anesthetics on the hemodynamic and metabolic alterations induced by the calcium ionophore A23187 were studied using isolated liver perfusion in fasted rats. Halothane, isoflurane and sevoflurane maintained basal hepatic flow, reduced oxygen consumption, and transiently enhanced net lactate production. All anesthetics significantly attenuated the decreases in hepatic flow and oxygen consumption after the administration of A23187. Volatile anesthetics may attenuate the hepatic vasoconstriction and oxygen debt induced by intracellular calcium overload. Less