Petrovich D R, Finkelstein S, Waring A J, Farber J L
J Biol Chem. 1984 Nov 10;259(21):13217-23.
An accelerated degradation of phospholipid is the likely basis of irreversible cell injury in ischemia, and the membranes of the endoplasmic reticulum of the liver are a convenient system with which to study the effect of such a disturbance on the structure and function of cellular membranes. In the present report, electron spin resonance spectroscopy has been used to evaluate changes in the molecular ordering of microsomal membrane phospholipids in the attempt to relate the loss of lipid to alterations in membrane structure. The order parameter, S, was calculated from spectra reflecting the anisotropic motion of 12-doxyl stearic acid incorporated into normal and 3-h ischemic microsomal membranes. Over the temperature range 4-40 degrees C, the molecular order (S) of ischemic membranes was increased by 8-10%. This increase was reproduced in the ordering of the phospholipids in liposomes prepared from total lipid extracts of the same membranes. In contrast, after removal of the neutral lipids, liposomes prepared from phospholipids of ischemic and control membranes had the same molecular order. There were no differences in the phospholipid species of control and ischemic membranes or in the fatty acid composition of the phospholipids. In the neutral lipid fraction of ischemic membranes, however, triglycerides and cholesterol were increased compared to control preparations. There were no free fatty acids. The total cholesterol content of the liver was unchanged after 3 h of ischemia. The cholesterol-to-phospholipid ratio of ischemic membranes, however, was increased by 22% from 0.258 to 0.315 as a consequence of the loss of phospholipid. Addition of cholesterol to the control total lipid extracts to give a cholesterol-to-phospholipid ratio the same as in ischemic membranes resulted in liposomes with order parameters similar to those of liposomes prepared from ischemic total lipids. It is concluded that the degradation of the phospholipids of the microsomal membrane results in a relative increase in the cholesterol-to-phospholipid ratio. This is accompanied, in turn, by an increased molecular order of the residual membrane phospholipids.
磷脂加速降解可能是缺血时不可逆细胞损伤的基础，而肝内质网的膜是研究这种干扰对细胞膜结构和功能影响的便利系统。在本报告中，电子自旋共振光谱已被用于评估微粒体膜磷脂分子有序性的变化，试图将脂质损失与膜结构改变联系起来。序参数S是根据反映掺入正常和3小时缺血微粒体膜中的12 - 脱氧硬脂酸各向异性运动的光谱计算得出的。在4 - 40℃温度范围内，缺血膜的分子有序性（S）增加了8 - 10%。这种增加在由相同膜的总脂质提取物制备的脂质体中磷脂的有序性中得到了重现。相比之下，去除中性脂质后，由缺血和对照膜的磷脂制备的脂质体具有相同的分子有序性。对照膜和缺血膜的磷脂种类或磷脂的脂肪酸组成没有差异。然而，在缺血膜的中性脂质部分，与对照制剂相比，甘油三酯和胆固醇增加。没有游离脂肪酸。缺血3小时后肝脏的总胆固醇含量未改变。然而，由于磷脂损失，缺血膜的胆固醇与磷脂比值从0.258增加到0.315，增加了22%。向对照总脂质提取物中添加胆固醇，使其胆固醇与磷脂比值与缺血膜相同，得到的脂质体的序参数与由缺血总脂质制备的脂质体相似。结论是微粒体膜磷脂的降解导致胆固醇与磷脂比值相对增加。这反过来又伴随着残余膜磷脂分子有序性的增加。
