Modulation of calcium current by ATP in guinea-pig adrenal chromaffin cells |
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Authors: | Ken-ichi Otstuguro Toshio Ohta Shigeo Ito Yoshikazu Nakazato |
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Affiliation: | (1) Laboratory of Pharmacology, Graduate School of Veterinary Medicine, Hokkaido University, 060 Sapporo, Japan |
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Abstract: | The effects of extracellular adenosine 5-triphosphate (ATP) on voltage-dependent Ca2+ currents were examined using the whole-cell voltage-clamp technique in guinea-pig isolated adrenal chromaffin cells. ATP (500 M) reversibly suppressed Ca2+ currents in the presence of 5 mM Ca2+ in the extracellular solution. The inhibitory effect of ATP on Ca2+ currents tended to increase with increases in the peak amplitude of ATP-evoked current when the intracellular solution contained 0.1 or 1 mM ethylenebis(oxonitrilo)tetraacetate(EGTA). Using the intracellular solution containing 10 mM EGTA, on the other hand, the inhibitory efftect did not change regardless of the amplitude of current responses to ATP In the presence of 10 mM Ba2+, ATP (100 mol/l). reduced Ba2+ currents in a manner similar to Ca2+ currents. This reduction was decreased by dialysis of cells with the internal solution containing guanosine 5-O-(2-thiodiphosphate) (GDP [-S]; 1 mM) or guanosine 5-O-(3-thiotriphos-phate) (GTP [-S]; 100 mol/l). A depolarizing prepulse channels. In addition, ATP seems to modulate Ca2+ channels via the pathway related to G-protein. Adenine nucleotides and adenosine may play a role in controlling secretory activity in guinea-pig adrenal chromaffin cells. |
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Keywords: | Adenine nucleotide Adenosine Chromaffin cells Calcium channels G-prooein Whole-cell voltage-clamp |
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