Evidence on the role of three calcium pools in Ca-ionophore A23187-stimulated rat blood platelet aggregation.
The effect of Ca-ionophore A23187 on activation of rat blood platelets was investigated to elucidate the involvement of extracellular and intracellular Ca2+ ions. Platelet aggregation induced by 10 concentrations of the stimulus was studied in Ca-free medium as well as in the presence of EGTA and/or calcium. In Ca-free medium, A23187 induced platelet aggregation in a dose-dependent way; the mean effective concentration was 1.43 +/- 0.08 mumol/l. The stimulatory effect of ionophore was potentiated by addition of 0.01 and 0.1 mM calcium and inhibited when the calcium concentration was increased to 1 mmol/l. In the presence of EGTA, A23187-stimulated aggregation of isolated rat platelets was recorded only at a 10-times higher ionophore concentration and was then reduced to 30% in comparison with aggregation in Ca-free medium. The inhibitory effect of 1 mM EGTA was abolished by addition of 2 mM calcium. We suggest the participation of at least three calcium pools in the stimulation of rat platelets by A23187, i.e. the extracellular pool, the membrane-associated pool and the pool displacing calcium intracellularly.
Jancinová
V
V
Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Czechoslovakia.
Nosál
R
R
Petríková
M
M
D000818:Animals; D000001:Calcimycin / Q000008:administration & dosage / Q000494:pharmacology*; D002118:Calcium / Q000097:blood* / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D000001:Calcimycin; D004533:Egtazic Acid; D002118:Calcium