The regulation of aortic endothelial cells by purines and pyrimidines involves co‐existing P2y‐purinoceptors and nucleotide receptors linked to phospholipase C

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Abstract
1 We have examined the phospholipase C responses in bovine aortic endothelial cells to purines (ATP, ADP and analogues) and the pyrimidine, uridine triphosphate (UTP). 2 The cells responded to purines in a manner consistent with the presence of P2y purinoceptors; both 2-methylthioadenosine 5′-triphosphate (2MeSATP) and adenosine 5′-0-(2-thiodiphosphate) (ADPβS) were potent agonists (EC50 0.41 μm and 0.85 μm respectively) while β, γ-methylene ATP at 300 μm was not. 3 The cells also responded to UTP. The maximal response to UTP was less than that for either 2MeSATP and ADPβS while adenosine 5′-0-(3-thiotriphosphate) (ATPγS) gave the largest maximal response. 4 The concentration-effect curve to UTP was additive in the presence of either 2MeSATP or ADPβS. However, the concentration-effect curves to ATP7S reached the same maximum in the presence or absence of UTP. 5 Suramin, at concentrations between 10 μm and 100 μm was a competitive antagonist for the response to ADPβS and 2MeSATP but not the response to UTP. 6 The results show that there are two separate, co-existing, receptor populations: P2y-purinoceptors (responding to purines) and nucleotide receptors (responding to both purines and pyrimidines). We conclude that purines such as ATP/ADP may regulate aortic endothelial cells by interacting with two phospholipase C-linked receptors.