Koyama T, Kinjo M, Araiso T
Research Institute of Applied Electricity, Hokkaido University, Saporo, Japan.
Adv Exp Med Biol. 1989;248:763-7. doi: 10.1007/978-1-4684-5643-1_86.
The effect of the mitochondrial membrane on the oxygen supply to the interior of mitochondria was analyzed with a cylinder model of diffusion. This estimation is based on the assumption that cytochrome a,a3 is distributed only on the inner surface of the mitochondrial inner membrane. The diffusion coefficient in the mitochondrial membrane was approximated from the fluorescently-determined viscosity of rat mitochondrial membrane. A pico-second time-resolved fluorometer at 37 degrees C gave values of 43.8 cp for intact mitochondria and 51.4 cp after phospholipase A2 treatment. Using the mean oxygen consumption rate of 10 ml O2/100 g tissue/sec in beating heart, oxygen gradients of 3.9 and 4.6 nmol was predicted across the intact and phospholipase-A2 treated mitochondrial membranes, respectively. The increased oxygen consumption during systole will yield oxygen gradients of 11.6 and 13.7 nmol. These gradients were much larger than the values estimated in a hypothetical case using the diffusion coefficient for the mitochondrial membrane of 1.5 x 10(-5) cm2/sec. The predicted oxygen gradient suggests a non-uniform distribution of oxygen in the myocardial cell and may be of importance in understanding the relationship between oxygen supply and myocardial function in hypoxia. Phospholipase A2, which is known to be activated in ischemia, destroys the microstructure of myocardial cells, seems deleterious to oxygen transport to cytochrome a,a3.
利用扩散圆柱模型分析了线粒体膜对线粒体内部氧气供应的影响。该估算基于细胞色素a、a3仅分布在线粒体内膜内表面的假设。线粒体膜中的扩散系数根据大鼠线粒体膜荧光测定的粘度进行近似估算。在37℃下，皮秒时间分辨荧光计测得完整线粒体的值为43.8厘泊，磷脂酶A2处理后为51.4厘泊。利用跳动心脏中10 ml O2/100 g组织/秒的平均耗氧率，预测完整和磷脂酶A2处理的线粒体膜上的氧梯度分别为3.9和4.6纳摩尔。收缩期耗氧量增加将产生11.6和13.7纳摩尔的氧梯度。这些梯度远大于在假设情况下使用1.5×10(-5) cm2/秒的线粒体膜扩散系数估算的值。预测的氧梯度表明心肌细胞中氧的分布不均匀，这可能对理解缺氧时氧供应与心肌功能之间的关系具有重要意义。已知在缺血时被激活的磷脂酶A2会破坏心肌细胞的微观结构，似乎对氧向细胞色素a、a3的转运有害。
