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Antagonistic Effect of Na + and Mg 2+ on P 2z Purinoceptor‐Associated Pores in Dibutyryl Cyclic AMP‐Differentiated NG108‐15 Cells
Author(s) -
Song ShuLing,
Chueh SheauHuei
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67041694.x
Subject(s) - extracellular , intracellular , chemistry , biophysics , calcium , stimulation , cytosol , biochemistry , endocrinology , biology , enzyme , organic chemistry
The effect of replacement of extracellular Na + with N ‐methyl‐ d ‐glucamine (NMG) on P 2 receptor signaling pathways was investigated in dibutyryl cyclic AMP‐differentiated NG108‐15 cells. Benzoylbenzoic ATP (BzATP) dose‐dependently increased the cytosolic Ca 2+ concentration ([Ca 2+ ] i ) with an EC 50 value of 230 µ M . Replacement of Na + with NMG as well as removal of Mg 2+ from the bathing buffer potentiated ethidium bromide uptake, [Ca 2+ ] i increase, and 45 Ca 2+ uptake in response to ATP or BzATP. In contrast, in the presence of 5 m M Mg 2+ to limit the amount of ATP 4− , replacement of Na + with NMG had no effect on the ATP‐induced [Ca 2+ ] i increase but caused a markedly larger [Ca 2+ ] i increase when the calculated concentration of ATP 4− was >10 µ M . The calculated EC 50 value for ATP 4− stimulation of the [Ca 2+ ] i increase was 23 µ M in NG108‐15 cells. In vascular smooth muscle cells, intracellular Ca 2+ release was the major pathway for the ATP‐induced [Ca 2+ ] i increase; both removal of Mg 2+ 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 Mg 2+ in dibutyryl cyclic AMP‐differentiated NG108‐15 cells.