Heart and Circulatory Unit, Department of Biomedical Sciences; Mitochondrial Research Laboratory, Department of Anaesthesia Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
Am J Physiol Regul Integr Comp Physiol. 2012 Jul 1;303(1):R94-100. doi: 10.1152/ajpregu.00044.2012. Epub 2012 May 2.
Nitric oxide (NO) and prostaglandins (PG) together play a role in regulating blood flow during exercise. NO also regulates mitochondrial oxygen consumption through competitive binding to cytochrome-c oxidase. Indomethacin uncouples and inhibits the electron transport chain in a concentration-dependent manner, and thus, inhibition of NO and PG synthesis may regulate both muscle oxygen delivery and utilization. The purpose of this study was to examine the independent and combined effects of NO and PG synthesis blockade (L-NMMA and indomethacin, respectively) on mitochondrial respiration in human muscle following knee extension exercise (KEE). Specifically, this study examined the physiological effect of NO, and the pharmacological effect of indomethacin, on muscle mitochondrial function. Consistent with their mechanism of action, we hypothesized that inhibition of nitric oxide synthase (NOS) and PG synthesis would have opposite effects on muscle mitochondrial respiration. Mitochondrial respiration was measured ex vivo by high-resolution respirometry in saponin-permeabilized fibers following 6 min KEE in control (CON; n = 8), arterial infusion of N(G)-monomethyl-L-arginine (L-NMMA; n = 4) and Indo (n = 4) followed by combined inhibition of NOS and PG synthesis (L-NMMA + Indo, n = 8). ADP-stimulated state 3 respiration (OXPHOS) with substrates for complex I (glutamate, malate) was reduced 50% by Indo. State 3 O(2) flux with complex I and II substrates was reduced less with both Indo (20%) and L-NMMA + Indo (15%) compared with CON. The results indicate that indomethacin reduces state 3 mitochondrial respiration primarily at complex I of the respiratory chain, while blockade of NOS by L-NMMA counteracts the inhibition by Indo. This effect on muscle mitochondria, in concert with a reduction of blood flow accounts for in vivo changes in muscle O(2) consumption during combined blockade of NOS and PG synthesis.
一氧化氮 (NO) 和前列腺素 (PG) 共同在运动过程中调节血流。NO 还通过与细胞色素-c 氧化酶的竞争性结合来调节线粒体的耗氧量。吲哚美辛以浓度依赖的方式解偶联并抑制电子传递链，因此，NO 和 PG 合成的抑制可能调节肌肉的氧输送和利用。本研究的目的是研究在膝关节伸展运动 (KEE) 后，NO 和 PG 合成的阻断 (分别为 L-NMMA 和吲哚美辛) 对人体肌肉中线粒体呼吸的独立和联合作用。具体而言，本研究研究了 NO 的生理作用以及吲哚美辛的药理学作用对肌肉线粒体功能的影响。与它们的作用机制一致，我们假设一氧化氮合酶 (NOS) 的抑制和 PG 合成的抑制对肌肉线粒体呼吸会产生相反的影响。在对照 (CON；n = 8)、动脉输注 N(G)-单甲基-L-精氨酸 (L-NMMA；n = 4) 和 Indo (n = 4) 后，用高分辨率呼吸计在皂素通透纤维中离体测量 KEE 后 6 分钟的线粒体呼吸，随后进行 NOS 和 PG 合成的联合抑制 (L-NMMA + Indo，n = 8)。用复合物 I (谷氨酸、苹果酸) 的底物刺激 ADP 刺激的状态 3 呼吸 (OXPHOS) 减少了 50%吲哚美辛。与 CON 相比，Indo 减少了状态 3 O2 通量与复合物 I 和 II 底物的 20%，L-NMMA + Indo 减少了 15%。结果表明，吲哚美辛主要减少呼吸链复合物 I 的状态 3 线粒体呼吸，而 L-NMMA 对 NOS 的阻断抵消了 Indo 的抑制作用。这种对肌肉线粒体的影响，与血流减少一起，解释了在联合阻断 NOS 和 PG 合成期间肌肉耗氧量的体内变化。
