title: Antagonistic effect of Na+ and Mg2+ on P2z purinoceptor-associated pores in dibutyryl cyclic AMP-differentiated NG108-15 cells.
abstract: The effect of replacement of extracellular Na+ with N-methyl-D-glucamine (NMG) on P2 receptor signaling pathways was investigated in dibutyryl cyclic AMP-differentiated NG108-15, cells. Benzoylbenzoic ATP (BzATP) dose-dependently increased the cytosolic Ca2+ concentration ([Ca2+]i) with an EC50 value of 230 microM. Replacement of Na+ with NMG as well as removal of Mg2+ from the bathing buffer potentiated ethidium bromide uptake, [Ca2+]i increase, and 45Ca2+ uptake in response to ATP or BzATP. In contrast, in the presence of 5 mM Mg2+ to limit the amount of ATP4-, replacement of Na+ with NMG had no effect on the ATP-induced [Ca2+]i increase but caused a markedly larger [Ca2+]i increase when the calculated concentration of ATP4- was > 10 microM. The calculated EC50 value for ATP4- stimulation of the [Ca2+]i increase was 23 microM in NG108-15 cells. In vascular smooth muscle cells, intracellular Ca2+ release was the major pathway for the ATP-induced [Ca2+]i increase; both removal of Mg2+ and replacement of Na+ with NMG did not affect the action of ATP. These data suggest that ATP(4-)-promoted pores are antagonized by Na+ and Mg2+ in dibutyryl cyclic AMP-differentiated NG108-15 cells.
authors.affiliation: Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China.
authors.forename: S L
authors.initials: SL
authors.lastname: Song
authors.forename: S H
authors.initials: SH
authors.lastname: Chueh
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000345:Affinity Labels; D000818:Animals; D001011:Aorta; D003994:Bucladesine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004996:Ethidium; D005910:Glioma; D006822:Hybrid Cells; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009447:Neuroblastoma; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*; D013552:Swine
chemical_list: D000345:Affinity Labels; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D003994:Bucladesine; D000255:Adenosine Triphosphate; D012964:Sodium; D004996:Ethidium; D008274:Magnesium; D002118:Calcium