Activation of a calcium- and pH-dependent phospholipase A2 by cyanide in PC12 cells

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Arachidonic Acid / metabolism
  • Calcium / pharmacology*
  • Cell Survival / drug effects
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Enzyme Activation / drug effects
  • Hydrogen-Ion Concentration
  • PC12 Cells / drug effects
  • PC12 Cells / enzymology*
  • PC12 Cells / metabolism
  • Phospholipases A / metabolism*
  • Phospholipases A2
  • Potassium Cyanide / pharmacology*
  • Rats


  • Arachidonic Acid
  • Egtazic Acid
  • Phospholipases A
  • Phospholipases A2
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Potassium Cyanide
  • Calcium