Pharmacological properties of ATP-sensitive purinergic receptors expressed in human G292 osteoblastic cells.

We characterized the pharmacological properties of P2 receptors expressed in G292 osteoblastic cells by studying the responses or changes in intracellular Ca(2+) level to P2 receptor agonists, antagonists and modulators. ATP induced robust responses in a concentration-dependent manner with EC(50) of 0.5+/-0.07 microM. While alpha,beta-methylene-ATP (alphabetameATP) and 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP) were ineffective, ADP mimicked the action of ATP with EC(50) of 0.7+/-0.2 microM. UTP and UDP also evoked responses with EC(50) of 2.0+/-0.4 microM and 0.5+/-0.1 microM respectively, but their responses were much smaller, resulting in an order of the response magnitude: ATP~ADP>>UTP~UDP. The responses evoked by ATP and ADP were blocked by pyridoxal-5'-phosphate-6-azophenyl-2,4,-disulfonate (PPADS) with IC(50) of 3.0+/-0.05 microM and 5.0+/-0.4 microM respectively, but not by suramin up to 30 microM. ATP-evoked responses were insensitive to inhibition by trinitrophenyl-ATP (TNP-ATP) and brilliant blue G. ADP-evoked responses were significantly inhibited by 2'-deoxy-N(6)-methyladenosine-3',5'-biphosphate (MRS2179) and 2-chloro-N(6)-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphate (MRS2279) with IC(50) of 48+/-1.9 microM and 7.7+/-0.9 microM respectively. Taken together, these results provide strong evidence for functional expression of ATP-sensitive P2Y receptors and particularly P2Y(1)-like receptor in G292 cells.