Dixon I M, Eyolfson D A, Dhalla N S
Division of Cardiovascular Sciences, St. Boniface General Hospital Research Center, Winnipeg, Canada.
Am J Physiol. 1987 Nov;253(5 Pt 2):H1026-34. doi: 10.1152/ajpheart.1987.253.5.H1026.
Although the occurrence of intracellular Ca2+ overload is known to be an important factor in hypoxia-reoxygenation injury, the exact mechanisms for this abnormality are not presently clear. Since Na+-Ca2+ exchange in the sarcolemmal membrane is considered to be involved in Ca2+ efflux, this study was undertaken to examine the effect of hypoxia reoxygenation on this system. Isolated rat hearts were made hypoxic by perfusing with a substrate-free medium gassed with 95% N2-5% CO2 and then reperfused with oxygenated normal medium. Hypoxia was found to markedly increase the resting tension and depress the ability of the heart to generate contractile force; reoxygenation resulted in partial recovery of these parameters. Sarcolemmal vesicles were isolated from control, hypoxic, and hypoxia-reoxygenated hearts, and the Na+-dependent Ca2+ uptake activity was measured at different times of incubation as well as at different concentrations of calcium. Sarcolemmal ATP-dependent Ca2+ accumulation was also measured for the purpose of comparison. A significant decrease in Na+-dependent Ca2+ uptake was observed in preparations from hearts made hypoxic for 10 min. Reoxygenation of 10-min hypoxic hearts resulted in a further depression of Na+-Ca2+ exchange activity. ATP-dependent Ca2+ accumulation was also depressed in hypoxic as well as reoxygenated hearts. These results suggest a defect in the Na+-Ca2+ exchange system and the ATP-dependent Ca2+ pump in the heart sarcolemmal membrane, and this may contribute to the occurrence of intracellular Ca2+ overload and functional abnormalities due to hypoxia-reoxygenation injury.
虽然已知细胞内钙超载的发生是缺氧-复氧损伤的一个重要因素，但目前这种异常的确切机制尚不清楚。由于肌膜中的钠-钙交换被认为参与钙外流，因此进行本研究以检测缺氧复氧对该系统的影响。通过用含95%氮气-5%二氧化碳的无底物培养基灌注使离体大鼠心脏缺氧，然后用含氧的正常培养基再灌注。发现缺氧显著增加静息张力并降低心脏产生收缩力的能力；复氧导致这些参数部分恢复。从对照、缺氧和缺氧-复氧的心脏中分离出肌膜囊泡，并在不同孵育时间以及不同钙浓度下测量钠依赖性钙摄取活性。还测量了肌膜ATP依赖性钙积累以作比较。在缺氧10分钟的心脏制备物中观察到钠依赖性钙摄取显著降低。10分钟缺氧心脏的复氧导致钠-钙交换活性进一步降低。缺氧和复氧心脏中的ATP依赖性钙积累也降低。这些结果提示心脏肌膜中的钠-钙交换系统和ATP依赖性钙泵存在缺陷，这可能导致细胞内钙超载的发生以及缺氧-复氧损伤引起的功能异常。
