Antagonistic Effect of Na+ and Mg2+ on P2z Purinoceptor-Associated Pores in Dibutyryl Cyclic AMP-Differentiated NG108-15 Cells |
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Authors: | Shu-Ling Song Sheau-Huei Chueh |
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Institution: | Graduate Institute of Life Sciences and; Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China |
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Abstract: | 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 µM. 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 µM. The calculated EC50 value for ATP4? stimulation of the Ca2+]i increase was 23 µM 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 ATP4?-promoted pores are antagonized by Na+ and Mg2+ in dibutyryl cyclic AMP-differentiated NG108-15 cells. |
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Keywords: | P2 receptor ATP NG108-15 cells Cytosolic Ca2+ concentration |
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