Kammermeier H
Dept. of Physiology, Medical Faculty, RHTH Aachen.
Biomed Biochim Acta. 1987;46(8-9):S499-504.
Energy (ATP) dependent processes of the cell can in principle be divided into near equilibrium (high efficiency) processes, which depend on free energy (change) from ATP-hydrolysis and those not dependent on the free energy levels i.e. non-equilibrium processes. Due to the high efficiencies of the contractile process and the ion transport processes involved in excitation contracting coupling free energy dependence of these processes can be inferred. Though an apparent relationship between the free energy levels and performance can be observed in the early hypoxic failure and graded reoxygenation of isolated isometrically working rat hearts, EC-coupling alteration seem to preceed critical drop of free energy levels. These alterations appear not to be brought about by increasing cytosolic Pi. A pronounced negative staircase phenomenon in hypoxia accompanied by maintained free energy levels are interpreted in terms of a protective mechanism, which prevents critical drop of free energy levels of the cells at costs of their contractile performance.
细胞中依赖能量（ATP）的过程原则上可分为近平衡（高效率）过程和非平衡过程，前者依赖于ATP水解产生的自由能（变化），后者则不依赖于自由能水平。由于收缩过程和兴奋-收缩偶联中涉及的离子转运过程效率很高，因此可以推断出这些过程对自由能的依赖性。尽管在离体等长收缩的大鼠心脏早期缺氧衰竭和分级复氧过程中，可以观察到自由能水平与心脏功能之间存在明显关系，但兴奋-收缩偶联的改变似乎先于自由能水平的临界下降。这些改变似乎不是由胞质Pi增加引起的。缺氧时出现的明显负阶梯现象，同时自由能水平保持不变，这可以用一种保护机制来解释，即这种机制以细胞收缩功能为代价，防止细胞自由能水平的临界下降。
