PYRUVATE-ENHANCED PHOSPHORYLATION POTENTIAL AND INOTROPISM IN NORMOXIC AND POSTISCHEMIC ISOLATED WORKING HEART - NEAR-COMPLETE PREVENTION OF REPERFUSION CONTRACTILE FAILURE
PYRUVATE-ENHANCED PHOSPHORYLATION POTENTIAL AND INOTROPISM IN NORMOXIC AND POSTISCHEMIC ISOLATED WORKING HEART - NEAR-COMPLETE PREVENTION OF REPERFUSION CONTRACTILE FAILURE
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DOI：
10.1111/j.1432-1033.1989.tb14637.x
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发表时间：
1989-03-01
期刊：
影响因子：
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通讯作者：
HARTMAN, DA
中科院分区：
文献类型：
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作者：
BUNGER, R;MALLET, RT;HARTMAN, DA
在常氧、低流量缺血和再灌流条件下，用0.2mM丙酮酸和0.7mM~1.1mM去甲肾上腺素(0.7mM-1.1mM去甲肾上腺素)对豚鼠心脏进行细胞氧化还原，比较了细胞氧化还原的生物能量和血流动力学效应。5 mM葡萄糖(+5U/i胰岛素)+5μM乳酸为基础产能底物。为了稳定左室舒张末期压力，在所有条件下，心室充盈压保持在12cmH2O；这种预负荷控制使Frank-Starling对心室正性的影响最小化。通过将主动脉压降低到冠脉自身调节储备以下的水平(20-10cmH2O)来诱导全球低流量缺血。肌酸激酶的反应物，包括H+和其他关键代谢物，通过酶、高效液相和极谱技术测定。在常氧心脏，去甲肾上腺素对正性肌力、心率×压力乘积和氧耗量(MVO2)的刺激与胞浆磷酸化潜力([ATP]/([ADP]·[PI])的下降有关，由肌酸激酶平衡判断)。相反，过量的丙酮酸(5 MM)输注后，[ATP]/([ADP]·[PI])和心输出量显著增加，而细胞内磷酸盐减少，MVO2在相同条件下保持不变。在缺血后再灌流期间，丙酮酸可影响心肌梗死，并使MVO2、磷酸化电位和变力作用呈浓度依赖性增加。丙酮酸脱氢酶流量在再灌流充血时增加，然后在5-10 mM丙酮酸存在下，[ATP]/([ADP]·[PI])、收缩力量、心率×压力乘积和MVO2接近完全恢复。丙酮酸也可减轻缺血腺苷的降解。省略灌流介质中的葡萄糖使丙酮酸在缺血后的心脏中无效。同样，过量的乳酸(5-15 mM)或醋酸盐(5 MM)不能使再灌流的心脏恢复活力，即使有葡萄糖存在，MVO2和变力作用也会出现严重的抑制。显然，丙酮酸解离的亚细胞氧化还原操作刺激了线粒体的呼吸，并增加了低胞浆磷酸化电位的变力作用。这证明线粒体外[ADP]·[PI]/[ATP]比值是控制线粒体呼吸的主要因素。丙酮酸增强常氧和再灌流的正性肌力的机制可能是多因素的。亚细胞[NADH]/[NAD+]比值的热力学效应与胞浆[ATP]/([ADP]·[PI])比值在恒定(常氧)或升高(再灌流)MVO2时的升高相结合。在缺血后心脏，丙酮酸的作用需要葡萄糖的存在。有人认为，丙酮酸的能量化可以改善肌浆网的离子泵，从而改善后者对钙的处理，这反过来可能会增加收缩状态；改善磷酸盐固定导致的细胞内[PI]降低也可能是原因之一。此外，再灌注期间增加的丙酮酸脱氢酶流量似乎加速了缺血后心脏的细胞恢复活力和功能恢复。
Bioenergetic and hemodynamic consequences of cellular redox manipulations by 0.2–20 mM pyruvate were compared with those due to adrenergic stess (0.7–1.1 μM norepinephrine) using isolated working guinea‐pig hearts under the conditions of normoxia, low‐flow ischemia, and reperfusion. 5 mM glucose (+ 5 U/I insulin) + 5 μM lactate were the basal energy‐yielding substrates. To stabilize left ventricular enddiastolic pressure, ventricular filling pressure was held at 12 cmH2O under all conditions; this preload control minimized Frank‐Starling effects on ventricular inotropism. Global low‐flow ischemia was induced by reducing aortic pressure to levels (20–10 cmH2O) below the coronary autoregulatory reserve. Reactants of the creatine kinase, including H+and other key metabolites, were measured by enzymatic, HPLC, and polarographic techniques.In normoxic hearts, norepinephrine stimulations of inotropism, heart rate × pressure product, and oxygen consumption (MVO2) were associated with a fall in the cytosolic phosphorylation potential ([ATP]/([ADP] · [Pi])) as judged by the creatine kinase equilibrium. In contrast, infusion of excess pyruvate (5 mM) markedly increased [ATP]/([ADP] · [Pi]) and ventricular work output, while intracellular phosphate decreased; MVO2remained constant under the same conditions. During reperfusion following ischemia, pyruvate effected strking and concentration‐dependent increases in MVO2, phosphorylation potential, and inotropism. Pyruvate dehydrogenase flux was augmented during reperfusion hyperemia followed by near‐complete recoveries of [ATP]/([ADP] · [Pi]), contractile force, heart rate × pressure product, and MVO2in the presence of 5–10 mM pyruvate. Pyruvate also attenuated ischemic adenylate degradation. Omission of glucose from the perfusion medium rendered pyruvate ineffective in postischemic hearts. Similarly, excess lactate (5–15 mM) or acetate (5 mM) failed to reenergize reperfused hearts and severe depressions of MVO2and inotropism developed despite the presence of glucose. Apparently, subcellular redox manipulations by pyruvate dissociated stimulated mitochondrial respiration and increased inotropism from low cytosolic phosphorylation potentials. This was evidence against the extramitochondrial [ADP] · [Pi]/[ATP] ratio being the primary factor in the control of mitochondrial respiration.The mechanism of pyruvate enhancement of inotropism during normoxia and reperfusion is probably multifactorial. Thermodynamic effects on subcellular [NADH]/[NAD+] ratios are coupled with a rise in the cytosolic [ATP]/([ADP] · [Pi]) ratio at constant (normoxia) or increased (reperfusion) MVO2. In postischemic hearts the effect of pyruvate required the presence of glucose. It is proposed that pyruvate energization may improve ion pumping by the sarcoplasmic reticulum and hence Ca2+‐handling by the latter which, in turn, might increase the contractile state; decreased intracellular [Pi] due to improved phosphate fixation may also be contributory. In addition, augmented pyruvate dehydrogenase flux during reperfusion seemed to expedite cellular reenergization and functional recovery in the postischemic hearts.