Effects of cytosolic ATP and other nucleotides on Ca2+-activated K+ channels in cultured bovine adrenal chromaffin cells.
The effects of cytosolic ATP on Ca2+-dependent K+ (K(Ca)) channel activation in cultured bovine adrenal chromaffin cells were investigated by using single-channel recording patch-clamp techniques. Application of ATP to the intracellular surface of excised inside-out patches activated K(Ca) channels in a dose-dependent manner at 30 microM to 10 mM. The K(Ca) channels also were activated by 3 mM of adenosine 5'-O-(3'-thiotriphosphate) (ATPgammaS), a non-hydrolyzable analogue of ATP, but not by 5'-adenylylimidodiphosphate (AMP-PNP) (from 300 microM to 3 mM). Furthermore, other nucleotides also activated K(Ca) channels in inside-out patches. This modulation took place without addition of exogenous protein kinase and was dependent on the presence of Mg2+ in the bathing solution. Staurosporine, a non-specific kinase inhibitor, or H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide), a cAMP-dependent protein kinase inhibitor, was unable to alter ATP-mediated K(Ca) channel activation. Following complete removal of Mg2+, a higher concentration of ATP (10 mM) and other nucleotides was required to activate K(Ca) channels; however, Mg2+ was ineffective in altering the activation of K(Ca) channels by itself. It is concluded that intracellular ATP and other nucleotides activate K(Ca) channels directly. These nucleotides may regulate catecholamine release by changing the cell membrane potential in adrenal chromaffin cells.
Department of Nutrition, School of Medicine, University of Tokushima, Japan.
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C
Chen
H
H
Houchi
T
T
Tamaki
Y
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Nakaya
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000311:Adrenal Glands / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002417:Cattle; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D003600:Cytosol / Q000378:metabolism*; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009711:Nucleotides / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects*; D047428:Protein Kinase Inhibitors; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides
D004791:Enzyme Inhibitors; D007546:Isoquinolines; D009711:Nucleotides; D015221:Potassium Channels; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D019311:Staurosporine; D008274:Magnesium; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium