INSERM, U-769, Châtenay-Malabry, France.
J Physiol. 2010 Jul 1;588(Pt 13):2443-54. doi: 10.1113/jphysiol.2010.189670. Epub 2010 May 17.
Cardiomyocyte contractile function requires tight control of the ATP/ADP ratio in the vicinity of the myosin-ATPase and sarcoplasmic reticulum ATPase (SERCA). In these cells, the main systems that provide energy are creatine kinase (CK), which catalyses phosphotransfer from phosphocreatine to ADP, and direct adenine nucleotide channelling (DANC) from mitochondria to ATPases. However, it is not known how and when these complex energetic systems are established during postnatal development. We therefore studied the maturation of the efficacy with which DANC and CK maintain ATP/ADP-dependent SR and myofibrillar function (SR Ca(2+) pumping and prevention of rigor tension), as well as the maturation of mitochondrial oxidative capacity. Experiments were performed on saponin-skinned fibres from left ventricles of 3-, 7-, 21-, 42- and 63-day-old mice. Cardiomyocyte and mitochondrial network morphology were characterized using electron microscopy. Our results show an early building-up of energetic microdomains in the developing mouse heart. CK efficacy for myosin-ATPase regulation was already maximal 3 days after birth, while for SERCA regulation it progressively increased until 21 days after birth. Seven days after birth, DANC for these two ATPases was as effective as in adult mice, despite a non-maximal mitochondrial respiration capacity. However, 3 days after birth, DANC between mitochondria and myosin-ATPase was not yet fully efficient. To prevent rigor tension in the presence of working mitochondria, the myosin-ATPase needed more intracellular MgATP in 3-day-old mice than in 7-day-old mice (pMgATP(50) 4.03 +/- 0.02 and 4.36 +/- 0.07, respectively, P < 0.05), whereas the intrinsic sensitivity of myofibrils to ATP (when mitochondria were inhibited) was similar at both ages. This may be due to the significant remodelling of the cytoarchitecture that occurs between these ages (cytosolic space reduction, formation of the mitochondrial network around the myofibrils). These results reveal a link between the maturation of intracellular energy pathways and cell architecture.
心肌细胞的收缩功能需要严格控制肌球蛋白-ATP 酶和肌浆网 ATP 酶（SERCA）附近的 ATP/ADP 比值。在这些细胞中，提供能量的主要系统是肌酸激酶（CK），它催化磷酸从磷酸肌酸转移到 ADP，以及线粒体到 ATP 酶的直接腺嘌呤核苷酸通道（DANC）。然而，目前尚不清楚这些复杂的能量系统在出生后发育过程中是如何以及何时建立的。因此，我们研究了 DANC 和 CK 维持 ATP/ADP 依赖性 SR 和肌纤维功能（SR Ca(2+)泵和防止强直张力）的效力以及线粒体氧化能力的成熟情况。实验在 3、7、21、42 和 63 天大的小鼠左心室的皂素处理的纤维上进行。使用电子显微镜对心肌细胞和线粒体网络形态进行了特征描述。我们的结果表明，在发育中的小鼠心脏中，早期建立了能量微区。3 天后，CK 对肌球蛋白-ATP 酶的调节效率已达到最大值，而对 SERCA 的调节效率则逐渐增加，直到出生后 21 天。出生后 7 天，DANC 对这两种 ATP 酶的作用与成年小鼠一样有效，尽管线粒体呼吸能力尚未达到最大值。然而，出生后 3 天，线粒体与肌球蛋白-ATP 酶之间的 DANC 尚未完全有效。为了在有工作线粒体的情况下防止强直张力，肌球蛋白-ATP 酶在 3 天大的小鼠中比在 7 天大的小鼠中需要更多的细胞内 MgATP（pMgATP(50) 4.03 +/- 0.02 和 4.36 +/- 0.07，分别，P < 0.05），而肌纤维对 ATP 的固有敏感性（当线粒体被抑制时）在这两个年龄时相似。这可能是由于这两个年龄段之间细胞结构的显著重塑（细胞溶胶空间减少，线粒体围绕肌纤维形成网络）所致。这些结果揭示了细胞内能量途径和细胞结构成熟之间的联系。
