Identification of potent P(2Y)-purinoceptor agonists that are derivatives of adenosine 5'-monophosphate

1. A series of chain-extended 2-thioether derivatives of adenosine monophosphate were synthesized and tested as agonists for activation of the phospholipase C-linked P(2Y)-purinoceptor of turkey erythrocyte membranes, the adenylyl cyclase-linked P(2Y)-purinoceptor of C6 rat glioma cells, and the cloned human P(2U)-receptor stably expressed in 1321N1 human astrocytoma cells. 2. Although adenosine monophosphate itself was not an agonist in the two P(2Y)-purinoceptor test systems, eleven different 2-thioether-substituted adenosine monophosphate analogues were full agonists. The most potent of these agonists, 2-hexylthio AMP, exhibited an EC₅₀ value of 0.2 nM for activation of the C6 cell receptor. This potency was 16,000 fold greater than that of ATP and was only 10 fold less than the potency of 2-hexylthio ATP in the same system. 2-hexylthio adenosine was inactive. 3. Monophosphate analogues that were the most potent activators of the C6 cell P(2Y)-purinoceptor were also the most potent activators of the turkey erythrocyte P(2Y)-purinoceptor. However, agonists were in general more potent at the C6 cell receptor, and potency differences varied between 10 fold and 300 fold between the two receptors. 4. Although 2-thioether derivatives of adenosine monophosphate were potent P(2Y)-purinoceptor agonists no effect of these analogues on the human P(2U)-purinoceptor were observed. 5. These results support the view that a single monophosphate is sufficient and necessary for full agonist activity at P(2Y)-purinoceptors, and provide insight for strategies for development of novel P(2Y)-purinoceptor agonists of high potency and selectivity.