J. Geiger et al., LIGAND SPECIFICITY AND TICLOPIDINE EFFECTS DISTINGUISH 3 HUMAN PLATELET ADP RECEPTORS, European journal of pharmacology, 351(2), 1998, pp. 235-246
Human platelets express adenosine 5'-diphosphate (ADP)-specific purino
ceptors of the P-2X and P-2Y receptor superfamily, but their structure
, diversity, and precise pharmacological profile is not well understoo
d. Here, functional assays with intact platelets and well-characterize
d nucleotide derivatives were performed in order to characterize the l
igand specificity of these platelet-specific purinoceptors. For the si
gnalling pathways investigated (aggregation, rapid Ca2+-influx, desens
itization of Ca2+-influx, Ca2+-mobilization, inhibition of adenylyl cy
clase), significant differences in ligand specificity were demonstrate
d. ADP activated all purinoceptors of human platelets, while adenosine
5'-triphosphate (ATP) was a weak agonist for the P-2X receptor and an
antagonist for the P-2Y receptors, The ADP-receptor pathway-antagonis
t ticlopidine inhibited ADP-evoked aggregation and adenylyl cyclase in
hibition but did not affect platelet purinoceptors associated with Ca2
+-influx and Ca2+-mobilization. These results indicate the presence of
three distinct ADP-selective purinoceptors on human platelets. (C) 19
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