The regulation of aortic endothelial cells by purines and pyrimidines involves co‐existing P 2y ‐purinoceptors and nucleotide receptors linked to phospholipase C

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 P 2y purinoceptors; both 2‐methylthioadenosine 5′‐triphosphate (2MeSATP) and adenosine 5′‐0‐(2‐thiodiphosphate) (ADPβS) were potent agonists (EC 50 0.41 μ m and 0.85 μ m respectively) while β, γ‐methylene ATP at 300 μ m 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 μ m and 100 μ m 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: P 2y ‐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.