title: Activation of a calcium- and pH-dependent phospholipase A2 by cyanide in PC12 cells.
abstract: 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.
authors.affiliation: Department of Pharmacology and Toxicology, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, Indiana 47907-1334.
authors.forename: C W
authors.initials: CW
authors.lastname: Yang
authors.forename: A
authors.initials: A
authors.lastname: Rathinavelu
authors.forename: J L
authors.initials: JL
authors.lastname: Borowitz
authors.forename: G E
authors.initials: GE
authors.lastname: Isom
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D016716:PC12 Cells / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011190:Potassium Cyanide / Q000494:pharmacology*; D051381:Rats
chemical_list: D016718:Arachidonic Acid; D004533:Egtazic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D011190:Potassium Cyanide; D002118:Calcium