title: Two-step mobilization of arachidonic acid in platelet activation induced by low concentrations of TP 82, a monoclonal antibody against CD9 antigen.
abstract: Arachidonic acid mobilization in platelets activated by low concentrations (less than or equal to 1.6 micrograms/ml) of TP 82, a monoclonal antibody against CD9, appears to consist of two distinct phases. In the first phase, limited arachidonic acid release occurs concomitantly with a shape change induced by TP 82. This appears to be dependent upon phospholipase A2 activation, since it is well preserved in the presence of aspirin, which completely blocked both intracellular Ca2+ elevation and phosphatidic acid formation which would indicate phospholipase C activation. The Na+ Exchange was also found to participate in the first phase of arachidonic acid mobilization, since extracellular Na+ depletion and ethylisopropylamiloride, a specific inhibitor of the Na+/H+ exchanger, effectively blocked this limited mobilization of arachidonic acid. The second, much larger, phase of arachidonic acid mobilization occurs with the beginning of platelet aggregation. A limited amount of thromboxane A2 formed during the first phase of arachidonic acid release plays an important role in induction of the massive arachidonic mobilization in the second phase. Factors, as yet unidentified, also appear to work synergistically with thromboxane A2 to induce the full picture of arachidonic acid mobilization.
authors.affiliation: Department of Clinical and Laboratory Medicine, Yamanashi Medical College, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ozaki
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: Y
authors.initials: Y
authors.lastname: Yatomi
authors.forename: M
authors.initials: M
authors.lastname: Higashihara
authors.forename: S
authors.initials: S
authors.lastname: Kume
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000502:physiology*; D000943:Antigens, Differentiation / Q000502:physiology*; D001095:Arachidonic Acids / Q000097:blood*; D001792:Blood Platelets / Q000502:physiology*; D002118:Calcium / Q000097:blood; D002352:Carrier Proteins / Q000097:blood; D005456:Fluorescent Dyes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006893:Hydroxyeicosatetraenoic Acids / Q000097:blood; D007700:Kinetics; D008562:Membrane Glycoproteins; D008954:Models, Biological; D010710:Phosphates / Q000097:blood; D010712:Phosphatidic Acids / Q000097:blood; D010741:Phospholipases A / Q000097:blood; D054467:Phospholipases A2; D015539:Platelet Activation; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers; D060245:Tetraspanin 29; D010738:Type C Phospholipases / Q000097:blood
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D001095:Arachidonic Acids; C554869:CD9 protein, human; D002352:Carrier Proteins; D005456:Fluorescent Dyes; D006893:Hydroxyeicosatetraenoic Acids; D008562:Membrane Glycoproteins; D010710:Phosphates; D010712:Phosphatidic Acids; D010980:Platelet Membrane Glycoproteins; D017923:Sodium-Hydrogen Exchangers; D060245:Tetraspanin 29; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D002118:Calcium