title: Does protein kinase C activation mediate thrombin-induced arachidonate release in human platelets?
abstract: Thrombin stimulated rapid formation of diacylglycerol, inositol 1,4,5-trisphosphate (IP3) and thromboxane B2 (TXB2) in human platelets. Formation of diacylglycerol and IP3 appeared to precede that of TXB2. Activation of protein kinase C by diacylglycerol combining with Ca+2 mobilization by IP3 has been implicated in mediating arachidonate release. However, addition of the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) to platelet suspension did not inhibit thrombin-stimulated arachidonate release and TXB2 synthesis, whereas addition of the Ca+2 antagonist, 3,4,5-trimethoxybenzoic acid 8-(diethylamino) octyl ester (TMB-8) or the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) abolished arachidonate release. The correlation of IP3 production with arachidonate release on increasing the concentrations of thrombin was further examined. IP3 production reached near maximum at 0.2 U/ml, whereas TXB2 synthesis continued to increase at 1 U/ml. These results suggest that protein kinase C activation may not mediate arachidonate release and that Ca+2 mobilization by IP3 may only partially account for arachidonate release in platelets stimulated with relatively high concentrations of thrombin.
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000097:blood*; D001792:Blood Platelets / Q000502:physiology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood; D004789:Enzyme Activation; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000097:blood*; D013449:Sulfonamides / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology*; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D001095:Arachidonic Acids; D007295:Inositol Phosphates; D007546:Isoquinolines; D010879:Piperazines; D013449:Sulfonamides; D016718:Arachidonic Acid; D000001:Calcimycin; D013929:Thromboxane B2; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; C017967:W 7; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; D013917:Thrombin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium