Calcium influx factor, further evidence it is 5, 6-epoxyeicosatrienoic acid.
We present evidence in astrocytes that 5,6-epoxyeicosatrienoic acid, a cytochrome P450 epoxygenase metabolite of arachidonic acid, may be a component of calcium influx factor, the elusive link between release of Ca2+ from intracellular stores and capacitative Ca2+ influx. Capacitative influx of extracellular Ca2+ was inhibited by blockade of the two critical steps in epoxyeicosatrienoic acid synthesis: release of arachidonic acid from phospholipid stores by cytosolic phospholipase A2 and cytochrome P450 metabolism of arachidonic acid. AAOCF3, which inhibits cytosolic phospholipase A2, blocked thapsigargin-stimulated release of arachidonic acid as well as thapsigargin-stimulated elevation of intracellular free calcium. Inhibition of P450 arachidonic acid metabolism with SKF525A, econazole, or N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide, a substrate inhibitor of P450 arachidonic acid metabolism, also blocked thapsigargin-stimulated Ca2+ influx. Nano- to picomolar 5, 6-epoxyeicosatrienoic acid induced [Ca2+]i elevation consistent with capacitative Ca2+ influx. We have previously shown that 5, 6-epoxyeicosatrienoic acid is synthesized and released by astrocytes. When 5,6-epoxyeicosatrienoic acid was applied to the rat brain surface, it induced vasodilation, suggesting that calcium influx factor may also serve a paracrine function. In summary, our results suggest that 5,6-epoxyeicosatrienoic acid may be a component of calcium influx factor and may participate in regulation of cerebral vascular tone.
Rzigalinski
B A
BA
Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298-0613, USA. brzigali@hsc.vcu.edu
Willoughby
K A
KA
Hoffman
S W
SW
Falck
J R
JR
Ellis
E F
EF
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017136:Ion Transport; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D051381:Rats; D015398:Signal Transduction; D019284:Thapsigargin / Q000037:antagonists & inhibitors / Q000494:pharmacology
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D016718:Arachidonic Acid; D019284:Thapsigargin; C040776:5,6-epoxy-8,11,14-eicosatrienoic acid; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; D010741:Phospholipases A; D054467:Phospholipases A2; D015126:8,11,14-Eicosatrienoic Acid; D002118:Calcium