Yang C W, Rathinavelu A, Borowitz J L, Isom G E
Department of Pharmacology and Toxicology, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, Indiana 47907-1334.
Toxicol Appl Pharmacol. 1994 Feb;124(2):262-7. doi: 10.1006/taap.1994.1031.
Previous studies suggested that alterations in phospholipid composition of plasma membranes may contribute to neuronal injury associated with cyanide-induced histotoxic hypoxia. This prompted a study of the effects of KCN on phospholipase A2 (PLA2), an enzyme which catalyzes breakdown of membrane phospholipids. PLA2 activity was measured by quantitating the release of [3H]arachidonic acid ([3H]AA) from rat pheochromocytoma (PC12) cells. KCN produced a time (1-15 min)- and concentration (0.5-10 mM)-dependent release of [3H]AA from the cells. When cells were incubated in Ca(2+)-free buffer, KCN (5 mM) was still able to release [3H]AA. In cells loaded with BAPTA, an intracellular Ca2+ chelator, cyanide-induced release of [3H]AA was blocked, indicating that mobilization of intracellular Ca2+ can activate the enzyme. The PLA2 inhibitors dibucaine (50 microM) and mepacrine (50 microM) inhibited KCN-mediated [3H]AA release. Incubation of PC12 cells in an extracellular pH of 6.50 reduced the KCN effect, whereas incubation at pH 7.90 enhanced [3H]AA release. These data indicate that in PC12 cells KCN activates a Ca(2+)- and pH-dependent PLA2 which may contribute to cyanide-induced cell damage.
以往的研究表明，质膜磷脂组成的改变可能与氰化物诱导的组织中毒性缺氧相关的神经元损伤有关。这促使人们对氰化钾（KCN）对磷脂酶A2（PLA2）的影响进行研究，PLA2是一种催化膜磷脂分解的酶。通过定量测定大鼠嗜铬细胞瘤（PC12）细胞中[3H]花生四烯酸（[3H]AA）的释放来测量PLA2活性。KCN可使细胞呈时间（1 - 15分钟）和浓度（0.5 - 10 mM）依赖性地释放[3H]AA。当细胞在无钙缓冲液中孵育时，KCN（5 mM）仍能释放[3H]AA。在装载了细胞内钙螯合剂BAPTA的细胞中，氰化物诱导的[3H]AA释放被阻断，这表明细胞内钙的动员可激活该酶。PLA2抑制剂丁卡因（50 microM）和米帕林（50 microM）可抑制KCN介导的[3H]AA释放。将PC12细胞在细胞外pH值为6.50的条件下孵育可降低KCN的作用，而在pH值为7.90的条件下孵育则可增强[3H]AA的释放。这些数据表明，在PC12细胞中，KCN可激活一种依赖于钙和pH的PLA2，这可能导致氰化物诱导的细胞损伤。
