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.