Protein kinase A mediates activation of ATP-sensitive K+ currents by CGRP in gallbladder smooth muscle.
The signal transduction mechanisms underlying the activation of ATP-sensitive potassium (KATP) current by calcitonin gene-related peptide (CGRP) in gallbladder smooth muscle were examined with intracellular microelectrode recording and whole cell patch-clamp techniques. In the intact gallbladder preparation, the adenylyl cyclase activator forskolin hyperpolarized the membrane potential and abolished spontaneous action potentials. This response was inhibited by the KATP channel blocker glibenclamide. CGRP (10 nM), forskolin (10 microM), the membrane-permeable adenosine 3',5'-cyclic monophosphate (cAMP) analogue adenosine 3',5'-cyclic monophosphothioate (Sp-cAMP[S]; 500 microM), and the catalytic subunit of protein kinase A (100 U/ml) activated glibenclamide-sensitive currents in enzymatically dissociated gallbladder smooth muscle cells. CGRP activation of potassium currents was prevented by dialysis of the cell cytoplasm with guanosine 5'-O-(2-thiodiphosphate) (5 mM) or a specific peptide inhibitor of protein kinase A (2.3 microM). Okadaic acid (5 microM), a phosphatase inhibitor, slowed the deactivation of the KATP current, following removal of CGRP. The results of this study indicate that CGRP hyperpolarizes gallbladder smooth muscle by elevation of cAMP and subsequent stimulation of protein kinase A.
Zhang
L
L
Department of Anatomy, College of Medicine, University of Vermont, Burlington 05405.
Bonev
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Mawe
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Nelson
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D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D004594:Electrophysiology; D004988:Ethers, Cyclic / Q000494:pharmacology; D005260:Female; D005704:Gallbladder / Q000187:drug effects / Q000502:physiology*; D005905:Glyburide / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D019319:Okadaic Acid; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology
D004988:Ethers, Cyclic; D015221:Potassium Channels; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D005576:Colforsin; D019319:Okadaic Acid; C023427:guanosine 5'-O-(2-thiodiphosphate); D000255:Adenosine Triphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D010744:Phosphoric Monoester Hydrolases; D015740:Calcitonin Gene-Related Peptide; D005905:Glyburide