title: Guanine nucleotides stimulate arachidonic acid release by phospholipase A2 in saponin-permeabilized human platelets.
abstract: GTP or GTP gamma S alone caused low but significant liberation of arachidonic acid in saponin-permeabilized human platelets but not in intact platelets. GTP or GTP gamma S also enhanced thrombin-induced [3H]arachidonic acid release in permeabilized platelets. Inhibitors of the phospholipase C (neomycin)/diacylglycerol lipase (RHC 80267) pathway for arachidonate liberation did not reduce the [3H]arachidonic acid release. The loss of [3H]arachidonate radioactivity from phosphatidylcholine was almost equivalent to the increase in released [3H]arachidonic acid, suggesting the hydrolysis of phosphatidylcholine by phospholipase A2. The effect of GTP gamma S was greater at lower Ca2+ concentrations. These data indicate that the release of arachidonic acid by phospholipase A2 in saponin-treated platelets may be linked to a GTP-binding protein.
mesh_terms: D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D006801:Humans; D010713:Phosphatidylcholines / Q000378:metabolism; D010740:Phospholipases / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D012503:Saponins / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
chemical_list: D001095:Arachidonic Acids; D010713:Phosphatidylcholines; D012503:Saponins; D013873:Thionucleotides; D016718:Arachidonic Acid; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D013917:Thrombin; D002118:Calcium