Gerber S H, Heyer C, Krüger C, Hagl S, Kübler W, Haass M
Department of Cardiology, University of Heidelberg, Germany.
J Mol Cell Cardiol. 1999 Jan;31(1):89-99. doi: 10.1006/jmcc.1998.0849.
It was the aim of the present study to investigate the influence of Bretschneider's cardioplegia on norepinephrine (NE) release [determined by high pressure liquid chromatography (HPLC) and electrochemical detection] in isolated perfused guinea-pig hearts. The following resulted were noted. (1) Calcium-dependent exocytotic NE release evoked by electrical field stimulation (12 Hz, 1 min) was completely suppressed after only 3 min of normothermic (37.5 degrees C) Bretschneider's cardioplegia. (2) Stop-flow ischemia is associated with a substantial calcium-independent, non-exocytotic NE release, which is regarded as a sodium-dependent carrier-mediated process. Accordingly, it is inhibited by blockers of the sodium/proton-exchanger (e.g. amiloride) and the neuronal uptake1-carrier (e.g. desipramine). Compared with stop-flow ischemia alone, cardioplegia with 3 min of Bretschneider's histidine-tryptophan-ketoglutarate (HTK)-solution preceding stop-flow enhanced NE release at all stop-flow durations (10-90 min) investigated (e.g. after 30 min of normothermic Bretschneider's cardioplegia: 1070+/-41 pmol/g, n = 45, v stop-flow alone: 764+/-48 pmol/g, n = 27, P<0.05). The NE concentrations determined in the cardiac effluent upon reperfusion followed a typical first order kinetic indicating that the transmitter release had already occurred during stop-flow. Hypothermia reduced NE release in a temperature-dependent manner down to intramyocardial temperatures of 2 7.5 degrees C. NE release evoked by Bretschneider's cardioplegia still exceeded that induced by stop-flow ischemia alone by up to 60%. The NE release evoked by Bretschneider's cardioplegia and stop-flow ischemia was calcium-independent. However, it was significantly reduced by desipramine and amiloride, but both agents had a more pronounced inhibitory effect on NE release evoked by stop-flow ischemia alone. (3) This difference may be due to an intrinsic effect of Bretschneider's HTK-solution, as continuous administration of normothermic Bretschneider's HTK-solution induced a substantial NE release which was neither calcium-dependent nor inhibited by blockade of either uptake1 or sodium/proton-exchange. It is concluded that Bretschneider's cardioplegia is not neuroprotective, as it even augments the stop-flow ischemia-induced nonexocytotic NE release.
本研究旨在探讨布雷施奈德心脏停搏液对离体灌注豚鼠心脏中去甲肾上腺素（NE）释放[通过高压液相色谱（HPLC）和电化学检测测定]的影响。结果如下：（1）常温（37.5℃）布雷施奈德心脏停搏液仅作用3分钟后，电场刺激（12Hz，1分钟）诱发的钙依赖性胞吐性NE释放就被完全抑制。（2）停流缺血与大量钙非依赖性、非胞吐性NE释放有关，这被认为是一种钠依赖性载体介导的过程。因此，它受到钠/质子交换体阻滞剂（如阿米洛利）和神经元摄取1载体阻滞剂（如地昔帕明）的抑制。与单纯停流缺血相比，在停流前用布雷施奈德组氨酸-色氨酸-酮戊二酸（HTK）溶液进行3分钟心脏停搏，在所有研究的停流持续时间（10 - 90分钟）内均增强了NE释放（例如，常温布雷施奈德心脏停搏30分钟后：1070±41pmol/g，n = 45，vs单纯停流：764±48pmol/g，n = 27，P<0.05）。再灌注时心脏流出液中测定的NE浓度遵循典型的一级动力学，表明递质释放已在停流期间发生。低温以温度依赖性方式降低NE释放，直至心肌内温度降至27.5℃。布雷施奈德心脏停搏液诱发的NE释放仍比单纯停流缺血诱发的NE释放高出60%。布雷施奈德心脏停搏液和停流缺血诱发的NE释放均与钙无关。然而，它被地昔帕明和阿米洛利显著降低，但这两种药物对单纯停流缺血诱发的NE释放具有更明显的抑制作用。（3）这种差异可能归因于布雷施奈德HTK溶液的内在作用，因为持续给予常温布雷施奈德HTK溶液会诱导大量NE释放，这种释放既不依赖于钙，也不受摄取1或钠/质子交换阻断的抑制。结论是，布雷施奈德心脏停搏液没有神经保护作用，因为它甚至会增强停流缺血诱导的非胞吐性NE释放。
