Intracellular ionized calcium mobilization of CD 9 monoclonal antibody-activated human platelets.
Cytoplasmic Ca2+ mobilization in human platelets triggered by a CD 9 monoclonal antibody, TP82, was monitored by the Ca2(+)-sensitive photoprotein, aequorin and Ca2(+)-sensitive fluorophores, fura 2 and quin 2. Aequorin-indicated Ca2+ values were proportional to the concentration of TP82, which was in inverse proportion to the lag time before the onset of platelet aggregation and serotonin release. When fura 2 was used as a Ca2+ indicator, above a threshold concentration, the TP82-induced intracellular Ca2+ value remained unchanged even with increasing concentration. The findings obtained with quin 2 were compatible with the fact that the TP82-induced intracellular Ca2+ increase was largely dependent on the secondary effect of thromboxane A2. These findings may be clues to explain the marked difference in the Ca2(+)-response characteristics between the fluorescent indicators and aequorin as well as the properties of TP82-induced platelet activation.
Yatomi
Y
Y
First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Higashihara
M
M
Ozaki
Y
Y
Kume
S
S
Kurokawa
K
K
D000331:Aequorin; D000634:Aminoquinolines; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000502:physiology*; D001572:Benzofurans; D001792:Blood Platelets / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D003593:Cytoplasm / Q000502:physiology; D016257:Fura-2; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins; D015539:Platelet Activation; D060245:Tetraspanin 29
D000634:Aminoquinolines; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D001572:Benzofurans; C554869:CD9 protein, human; D008562:Membrane Glycoproteins; D060245:Tetraspanin 29; D000331:Aequorin; C035738:Quin2-acetoxymethyl ester; D002118:Calcium; D016257:Fura-2