Hamman B L, Bittl J A, Jacobus W E, Allen P D, Spencer R S, Tian R, Ingwall J S
NMR Laboratory for Physiological Chemistry, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Am J Physiol. 1995 Sep;269(3 Pt 2):H1030-6. doi: 10.1152/ajpheart.1995.269.3.H1030.
To define the relation between phosphoryl transfer via creatine kinase (CK) and the ability of the intact beating heart to do work, we chemically inhibited CK activity and then measured cardiac performance under physiological and acute stress conditions. Isolated perfused rat hearts were exposed to iodoacetamide (IA) and subjected to one of three cardiac stresses: hypercalcemic (Ca2+ = 3 mM) buffer perfusion (n = 7), norepinephrine (2 mumol/min) infusion (n = 6), or hypoxic buffer perfusion (n = 5). IA decreased CK activity to near zero, measured in intact hearts by 31P magnetization transfer, and to 2% of control CK activity, measured in myocardial homogenates. The CK isoenzyme profile was unchanged, suggesting nonselective IA inhibition of all isoenzymes. Mitochondria isolated from IA-treated hearts had normal ADP:O ratios, state 3 respiratory rates, and unchanged acceptor and respiratory control ratios. Neither actomyosin adenosinetriphosphatase nor adenylate kinase activities were changed. After IA exposure, end-diastolic pressure, left ventricular developed pressure, and heart rate were unchanged for at least 30 min at physiological perfusion pressures, but large changes were observed during stress conditions. The increase in left ventricular developed pressure induced by hypercalcemic perfusion and by norepinephrine infusion decreased by 39 and 54%, respectively. During hypoxia, the rate of phosphocreatine depletion was decreased by 57%, left ventricular developed pressure declined, and end-diastolic pressure increased faster than in controls. These results show that inhibition of CK to < 2% of control activity by IA reduced contractile reserve by approximately 50%. We conclude that CK activity is essential for the expression of the full dynamic range of myocardial performance.
为了确定通过肌酸激酶（CK）的磷酸转移与完整跳动心脏做功能力之间的关系，我们通过化学方法抑制CK活性，然后在生理和急性应激条件下测量心脏功能。将离体灌注的大鼠心脏暴露于碘乙酰胺（IA），并施加三种心脏应激之一：高钙血症（Ca2+ = 3 mM）缓冲液灌注（n = 7）、去甲肾上腺素（2 μmol/min）输注（n = 6）或低氧缓冲液灌注（n = 5）。IA使CK活性降至接近零，通过31P磁化转移在完整心脏中测量，在心肌匀浆中测量时降至对照CK活性的2%。CK同工酶谱未改变，表明IA对所有同工酶的抑制是非选择性的。从IA处理的心脏中分离的线粒体具有正常的ADP:O比值、状态3呼吸速率，且受体和呼吸控制比值未改变。肌动球蛋白三磷酸腺苷酶和腺苷酸激酶活性均未改变。暴露于IA后，在生理灌注压力下，舒张末期压力、左心室舒张末压和心率至少30分钟未改变，但在应激条件下观察到了较大变化。高钙血症灌注和去甲肾上腺素输注诱导的左心室舒张末压增加分别降低了39%和54%。在低氧期间，磷酸肌酸消耗率降低了57%，左心室舒张末压下降，舒张末期压力比对照组增加得更快。这些结果表明，IA将CK抑制至对照活性的<2%可使收缩储备降低约50%。我们得出结论，CK活性对于心肌功能全动态范围的表达至关重要。
