PPADS: an antagonist at endothelial P_(2Y)-purinoceptors but not P_(2U)-purinoceptors

摘要

1 Bovine aortic endothelial (BAE) cells contain two co-existing receptors for extracellular ATP, the P_(2Y) and P_(2U)-purinoceptors. Here we have determined whether the proposed P_(2X)-purinoceptor antagonist, pyridoxalphosphate-6-azophenyl-2′, 4′-disulphonic acid (PPADS) could distinguish between these two receptor subtypes. 2 Cells labelled with myo-[2-~3H]-inositol were stimulated with increasing concentrations of either the P_(2Y)-agonist, 2MeSATP, or the P_(2Y)-agonist, UTP in the absence or presence of 30 μM PPADS. The accumulation of total [~3H]-inositol (poly)phosphates mediated by 2MeSATP was markedly attenuated by PPADS, whereas the response to UTP was not significantly affected. 3 Stimulation of BAE cells with increasing concentrations of ATP showed a reduced response in the presence of 10 μM PPADS, but this effect of the antagonist was not significant. By contrast, inhibition of the response to ADP was profound and highly significant. 4 These observations show that PPADS is not a selective P_(2X)-purinoceptor antagonist, but is able to distinguish between P_(2Y)- and P_(2U)-purinoceptors in BAE cells, and indicate that this compound may provide a useful tool in the study of multiple subtypes of P_2-purinoceptors. Furthermore the results are consistent with the hypothesis that ATP interacts with both receptor subtypes, but that the action of ADP is primarily at the P_(2Y)-purinoceptor in these endothelial cells.