Sa. Saeed et al., SYNERGISTIC INTERACTION OF A CALCIUM IONOPHORE, A23187, AND DOPAMINE IN HUMAN PLATELET-AGGREGATION, Medical science research, 25(4), 1997, pp. 219-221
This study was undertaken to investigate the mechanism(s) of platelet
aggregation induced by the synergistic action of dopamine (DA) and a C
a2+-ionophore A23187. DA showed no or little effect on aggregation ove
r a wide range of concentrations (up to 500 mu M), but did potentiate
the aggregation response of A23187. Aggregation induced by A23187 was
inhibited by calcium channel blockers (diltiazem and verapamil), recep
tor blockers (chlorpromazine and haloperidol) and cyclo-oxygenase inhi
bitor (indomethacin). However, the inhibitory effect of these blockers
was more marked (with a selectivity ratio of 1.5-28) in the aggregati
on induced by synergistic effect of A23187 and DA. A phosphatidylinosi
tol 3-kinase (PI 3-kinase) inhibitor, wortmannin (IC50; 25-30 nM), inh
ibited aggregation induced by either A23187 alone or A23187 plus DA. T
hese data suggest that A23187 and DA act synergistically and that this
synergistic effect on platelet aggregation is mediated through multip
le signalling pathways.