Protein kinase C inhibitors suppress disc-sphere changes of human platelets, as assessed with the shape-change parameter.
Changes in the shape of human platelets and the biochemical mechanism responsible were evaluated, using the shape-change parameter. Neither the Na+/H+ exchanger, nor intracellular or extracellular calcium ions (Ca2+) affected disc-sphere changes induced by low doses of thrombin. Treatment with inhibitors of Ca2+ mobilization, calmodulin or mysoin light-chain kinase had no significant effect on the shape change of platelets. Staurosporine and H-7, both of which are inhibitors of protein kinase C, inhibited disc-sphere changes at low concentrations. Moreover, calphostin C, a specific inhibitor of protein kinase C, effectively inhibited thrombin-induced shape change, as assessed by the shape-change parameter, in a dose-dependent manner. 1-Oleoyl-2-acetyl-glycerol and 1,2-dioctanoyl-glycerol, which are synthetic protein kinase C activators, induced shape changes similar to those induced by thrombin. A decrease in the surface area of platelet images on scanning electron micrographs was used to quantify the disc-sphere transformation. The mean platelet areas was significantly decreased after stimulation with thrombin or 1-oleoyl-2-acetyl-glycerol. Pretreatment with H-7 inhibited the thrombin-induced disc-sphere change, as assessed by changes in the platelet surface area. Our results obtained with various inhibitors suggest that thrombin-induced platelet change, as assessed by the shape-change parameter, are associated with activation of protein kinase C.
Department of Clinical and Laboratory Medicine, Yamanashi Medical College, Japan.
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Y
Ozaki
Y
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Jinnai
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Y
Yatomi
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Kume
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D016257:Fura-2 / Q000494:pharmacology; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D007546:Isoquinolines / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D010879:Piperazines / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D002147:Calmodulin; D007546:Isoquinolines; D010879:Piperazines; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D012964:Sodium; D011493:Protein Kinase C; D013917:Thrombin; D002118:Calcium; D016257:Fura-2