Schwertz D W, Halverson J, Isaacson T, Feinberg H, Palmer J W
Department of Pharmacology, University of Illinois College of Medicine, Chicago 60612.
J Mol Cell Cardiol. 1987 Jul;19(7):685-97. doi: 10.1016/s0022-2828(87)80377-2.
The effect of global ischemia on myocardial ventricular membrane phospholipids was evaluated using a modified Langendorff preparation. Isolated rat hearts were perfused at 37 degrees C with oxygenated Krebs Ringer solution or rendered ischemic by cessation of perfusion (10 min to 3 h). Longer periods of ischemia were assessed by incubating preperfused (10 min) intact hearts in non-oxygenated Krebs (37 degrees C) for 6 to 18 h. Ischemia-induced alterations in phosphatidylinositol levels and phosphoinositide-specific phospholipase C (PI PLC) activity were assessed in detail, since inositol phospholipids and PI-PLC play putative roles in the regulation of cell function and Ca2+ homeostasis. Decreases in major membrane phospholipids (phosphatidylcholine, phosphatidylserine, cardiolipin and sphingomyelin) were demonstrated after long ischemic periods (6 to 18 h). While periods of ischemia (3 h or less) induced no change in structural phospholipids, an elevation in lysophosphatidylcholine and free fatty acids was found by 1 h. Notably a significant increase in phosphatidylinositol content and an accompanying decrease in cytosolic PI PLC activity was detected by 30 mins of ischemia. Reduced enzymic activity was not due to altered in vitro activation or deactivation of PI-PLC, to a change in the Ca2+ requirement of the enzyme, or to translocation of the enzyme from the cytosol to a membrane fraction. The isolated rat heart made globally ischemic for 30 mins under conditions described for this investigation shows signs of irreversible injury i.e. increased cell Ca2+ content and inability to initiate and maintain rhythmic contraction upon reperfusion. Therefore, it is possible that altered phosphoinositide metabolism may contribute to the evolution of ischemia-elicited irreversible cell injury.
使用改良的Langendorff装置评估了全脑缺血对心肌细胞膜磷脂的影响。将离体大鼠心脏在37℃下用含氧的Krebs-Ringer溶液灌注，或通过停止灌注（10分钟至3小时）使其缺血。通过将预先灌注（10分钟）的完整心脏在无氧的Krebs溶液（37℃）中孵育6至18小时来评估更长时间的缺血。详细评估了缺血诱导的磷脂酰肌醇水平变化和磷脂酰肌醇特异性磷脂酶C（PI PLC）活性，因为肌醇磷脂和PI-PLC在细胞功能调节和Ca2+稳态中可能发挥作用。长时间缺血（6至18小时）后，主要膜磷脂（磷脂酰胆碱、磷脂酰丝氨酸、心磷脂和鞘磷脂）减少。虽然缺血期（3小时或更短）未引起结构磷脂的变化，但在1小时时发现溶血磷脂酰胆碱和游离脂肪酸升高。值得注意的是，缺血30分钟时检测到磷脂酰肌醇含量显著增加，同时胞质PI PLC活性下降。酶活性降低不是由于PI-PLC的体外激活或失活改变、酶对Ca²⁺需求的变化或酶从胞质溶胶向膜部分的转位。在本研究所述条件下全脑缺血30分钟的离体大鼠心脏显示出不可逆损伤的迹象，即细胞Ca²⁺含量增加，再灌注时无法启动和维持节律性收缩。因此，磷酸肌醇代谢改变可能导致缺血引发的不可逆细胞损伤的发展。
