The phospholipase A2-induced increase in the permeability of phospholipid membranes to Ca2+ and H+ ions.
The permeability of liposomes prepared from beef heart mitochondrial phospholipids was studied after treatment with phospholipase A2. The permeability to H+ ions was measured by recording the rate of change of pH in the external medium following an addition of an aliquot of alkali to liposomes with a highly buffered inner medium, while the penetration of Ca2+ ions into liposomes was measured in liposomes loaded with arsenazo III. There was a doubling of H+ permeability when the lysophospholipid content was increased to 2% by treatment with phospholipase A2, and a tripling at 4%. Entrapped sucrose leakage from liposomes became apparent at above 6% lysophospholipid. Treatment with phospholipase A2 stimulated Ca2+ penetration into liposomes driven by a valinomycin-induced diffusion potential or a nigericin-induced H+ gradient. The data are discussed in relation to the mechanism of damage to mitochondria occurring in Ca2+ overload as well as in phospholipase A2-induced cellular damage.
Eriksson
O
O
Institutionen för medicinsk kemi, Helsingfors Universitet.
Saris
N E
NE
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D006859:Hydrogen / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D008929:Mitochondria, Heart; D009550:Nigericin; D010740:Phospholipases / Q000494:pharmacology*; D010741:Phospholipases A / Q000494:pharmacology*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D008051:Lipid Bilayers; D010743:Phospholipids; D014634:Valinomycin; D006859:Hydrogen; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D009550:Nigericin; D002118:Calcium