Van Brussel E, Yang J J, Seraydarian M W
J Cell Physiol. 1983 Aug;116(2):221-6. doi: 10.1002/jcp.1041160214.
Previous studies on the energy metabolism of rat myocardial cells in culture supported the hypothesis that the creatine-phosphocreatine-creatine kinase system plays an important role in the intracellular transport of energy from the mitochondria to the myofibrils and in the regulation of energy production coupled to energy utilization in this model system. Effective functional compartmentation of ATP could result from the binding of creatine kinase to cellular organelles (e.g., myofibrils and mitochondria) such that high energy charge at the myofibrils is maintained by the reverse creatine kinase reaction, while phosphocreatine is synthesized mainly at the mitochondria in the forward creatine kinase reaction. It was, therefore, essential to demonstrate the presence of mitochondrial creatine kinase in the cultured myocardial cells to support this hypothesis, particularly since the mitochondrial creatine kinase was reportedly absent in fetal hearts. Using electrophoresis on cellulose acetate strips, the mitochondrial creatine kinase isozyme, as well as MM, MB, and BB isozymes, have now been demonstrated in myocardial cultures derived from neonatal rats. The mitochondrial creatine kinase increased with age in culture and with age of animal from which the culture is derived. Furthermore, the addition of creatine to culture media stimulates its synthesis. The mitochondrial creatine kinase isozyme was not detected in nonmuscle cells in culture derived from the neonatal rat hearts, nor in L6 muscle cell line. Phosphocreatine was present in all cells, but the regulation of energy metabolism and energy shuttle by creatine-phosphocreatine-creatine kinase could be operative only in the cells where the mitochondrial creatine kinase is present. This regulatory mechanism provides for an efficient system concomitant with the continuous energy demand of the myocardium; it is not ubiquitous and its development in myocardial cells seems to be triggered postnatally.
以往对培养的大鼠心肌细胞能量代谢的研究支持了这样一种假说，即肌酸 - 磷酸肌酸 - 肌酸激酶系统在该模型系统中，对于能量从线粒体到肌原纤维的细胞内转运以及能量产生与能量利用的偶联调节起着重要作用。三磷酸腺苷（ATP）有效的功能分隔可能源于肌酸激酶与细胞器（如肌原纤维和线粒体）的结合，这样通过肌酸激酶的逆反应可维持肌原纤维处的高能量状态，而磷酸肌酸主要是在肌酸激酶的正反应中于线粒体处合成。因此，为了支持这一假说，证明培养的心肌细胞中线粒体肌酸激酶的存在至关重要，特别是因为据报道胎儿心脏中不存在线粒体肌酸激酶。通过在醋酸纤维素条上进行电泳，现已在新生大鼠的心肌培养物中证实了线粒体肌酸激酶同工酶以及MM、MB和BB同工酶的存在。线粒体肌酸激酶在培养过程中随年龄增加而增加，并且与培养物所源自动物的年龄相关。此外，向培养基中添加肌酸会刺激其合成。在源自新生大鼠心脏的培养的非肌肉细胞以及L6肌肉细胞系中均未检测到线粒体肌酸激酶同工酶。磷酸肌酸存在于所有细胞中，但肌酸 - 磷酸肌酸 - 肌酸激酶对能量代谢和能量穿梭的调节仅在存在线粒体肌酸激酶的细胞中起作用。这种调节机制为伴随心肌持续能量需求的高效系统提供了保障；它并非普遍存在，其在心肌细胞中的发育似乎是在出生后被触发的。
