Two subtypes of G protein‐coupled nucleotide receptors, P2Y 1 and P2Y 2 are involved in calcium signalling in glioma C6 cells

In glioma C6 cells, the stimulation of P2Y receptors by ADP, ATP and UTP initiated an increase in the intracellular Ca 2+ concentration, in a process that involved the release of Ca 2+ from InsP 3 ‐sensitive store and the capacitative, extracellular Ca 2+ entry. The presence of external Ca 2+ was not necessary to elevate Ca 2+ . The rank order of potencies of nucleotide analogues in stimulating [Ca 2+ ] i was: 2MeSADP > ADP > 2MeSATP = 2ClATP > ATP > UTP. α,β‐Methylene ATP, adenosine and AMP were ineffective. ADP and UTP effects were additive, while actions of ATP and UTP were not additive on [Ca 2+ ] i increase. Similarly, cross‐desensitization between ATP and UTP but not between ADP and UTP occurred. Suramin, a non‐specific nucleotide receptors inhibitor, antagonized ATP‐, UTP‐ and ADP‐evoked Ca 2+ responses. PPADS, a selective antagonist of the P2Y 1 receptor‐generated InsP 3 accumulation, decreased ADP‐initiated Ca 2+ response with no effect on ATP and UTP. Pertussis toxin (PTX) reduced ADP‐ and ATP‐induced Ca 2+ increases. Short‐term treatment with TPA, inhibited both ATP and ADP stimulatory effects on [Ca 2+ ] i . ADP inhibited isoproterenol‐induced cyclic AMP accumulation. PTX blocked this effect, but PPADS did not. RT – PCR analysis revealed the molecular identity of P2Y receptors expressed by glioma C6 cells to be both P2Y 1 and P2Y 2 . It is concluded that both P2Y 1 and P2Y 2 receptors co‐exist in glioma C6 cells. ADP acts as agonist of the first, and ATP and UTP of the second one. Both receptors are linked to phospholipase C (PLC).British Journal of Pharmacology (2001) 132 , 393–402; doi: 10.1038/sj.bjp.0703843