Koyama T, Zhu M Y
Research Institute of Applied Electricity, Hokkaido University, Sapporo, Japan.
Adv Exp Med Biol. 1992;316:271-7. doi: 10.1007/978-1-4615-3404-4_31.
Mitochondria isolated from myocardium exposed to 30 minute ischemia followed by 30 minute reperfusion showed an increase in membrane viscosity and a decrease in wobbling angle of phospholipids, compared with those from the normally perfused myocardium in anesthetized open-chest rabbits. The values for the membrane viscosity were used to estimate the oxygen gradient across the lipid bilayers of mitochondrial membranes with a model of cylindrical diffusion. The effective diffusion coefficient for oxygen, DO2, was approximated to be 6.5 and 6.3 x 10(-5) cm2/sec in the control and ischemic-reperfused area, respectively, by comparing reported DO2 values with values for membrane viscosity. For the surface area of the inner mitochondrial membrane including cristae and for the oxygen consumption rate of the myocardium, reported values for rats and cats, respectively, were employed. Using these values, oxygen gradients across the lipid bilayers of mitochondrial lipid membranes were estimated to be only 0.055 and 0.057 nM in the control and 30 minute ischemic-reperfused myocardium, respectively. If the mitochondrial membranes are hydrated because of the ischemia-reperfusion, the absorption coefficient of the membrane to oxygen will decrease and the oxygen gradient will be increased. In the present study, however, the fluorescence life time of DPH, the hydrophobic fluorophore, showed no shortening despite the ischemia-reperfusion. Hence, no indication of membrane hydration was obtained.
与麻醉开胸兔正常灌注心肌分离的线粒体相比，从经历30分钟缺血再灌注30分钟的心肌中分离出的线粒体显示膜粘度增加，磷脂摆动角减小。膜粘度值用于通过圆柱扩散模型估计跨线粒体膜脂质双层的氧梯度。通过将报道的氧扩散系数（DO2）值与膜粘度值进行比较，在对照和缺血再灌注区域，氧的有效扩散系数DO2分别近似为6.5和6.3×10(-5) cm2/秒。对于包括嵴在内的线粒体内膜表面积和心肌的氧消耗率，分别采用大鼠和猫的报道值。利用这些值，在对照和30分钟缺血再灌注心肌中，跨线粒体脂质膜脂质双层的氧梯度估计分别仅为0.055和0.057 nM。如果线粒体膜因缺血再灌注而水合，膜对氧的吸收系数将降低，氧梯度将增加。然而，在本研究中，尽管存在缺血再灌注，疏水荧光团DPH的荧光寿命并未缩短。因此，未获得膜水合的迹象。
