Regulation of arachidonic acid release in vascular endothelium. Ca(2+)-dependent and -independent pathways.
Ca2+ metabolism and its relationship to arachidonic acid release were studied in cultured pig aortic endothelial cells. When cells were treated with bradykinin, a rapid rise in intracellular Ca2+ concentration ([Ca2+]i) occurred. Arachidonic acid release from cells prelabelled with [3H]arachidonic acid and subjected to flow-through conditions closely followed the changes in [Ca2+]i. Attenuation of the Ca2+ response by chelating extracellular and intracellular Ca2+ or by desensitization of receptors led to comparable attenuation of arachidonate release. Activation of protein kinase C inhibited Ca2+ mobilization in response to bradykinin and stimulated arachidonic acid release. Inhibition of protein kinase C had no effect on bradykinin-stimulated arachidonic acid release, suggesting that protein kinase C does not mediate the bradykinin response. The role of GTP-binding regulatory proteins (G-proteins) in mediating the bradykinin response was also investigated. Bradykinin-stimulated arachidonic acid release was not diminished by preincubation with pertussis toxin. Treatment with the G-protein activator AlF4- resulted in the release of a large pool of arachidonic acid and the formation of lysophospholipids. Combined treatment with AlF4- and bradykinin resulted in a greater than additive effect on arachidonic acid release. In contrast with bradykinin, AlF(4-)-stimulated arachidonic acid release was not dependent on the presence of extracellular Ca2+ or the mobilization of intracellular Ca2+. These results demonstrate Ca(2+)-dependent (bradykinin) and Ca(2+)-independent (AlF4-) pathways of phospholipase A2 activation.
Buckley
B J
BJ
Department of Medicine, Duke University Medical Center, Durham, NC 27710.
Barchowsky
A
A
Dolor
R J
RJ
Whorton
A R
AR
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002614:Chelating Agents; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism; D008246:Lysophospholipids / Q000096:biosynthesis; D011493:Protein Kinase C / Q000378:metabolism; D012969:Sodium Fluoride / Q000494:pharmacology; D019311:Staurosporine; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D002614:Chelating Agents; D008246:Lysophospholipids; D016718:Arachidonic Acid; D004533:Egtazic Acid; D012969:Sodium Fluoride; C058180:5,5'-dimethyl-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; D001920:Bradykinin; D002118:Calcium