Calcitonin gene-related peptide activated ATP-sensitive K+ currents in rabbit arterial smooth muscle via protein kinase A.
1. Whole-cell K+ currents activated by calcitonin gene-related peptide (CGRP) in smooth muscle cells enzymatically isolated from rabbit mesenteric arteries were measured in the conventional and perforated configurations of the patch clamp technique. The signal transduction pathway from CGRP receptors to activation of potassium currents was investigated. 2. CGRP (10 nM) activated a whole-cell current that was blocked by glibenclamide (10 microM), an inhibitor of ATP-sensitive K+ channels. Elevating intracellular ATP reduced glibenclamide-sensitive currents. CGRP increased the glibenclamide-sensitive currents by 3- to 6-fold in cells dialysed with 0.1 mM ATP, 3.0 mM ATP or in intact cells. The reversal potential of the glibenclamide-sensitive current in the presence of CGRP shifted with the potassium equilibrium potential, while its current-voltage relationship exhibited little voltage dependence. 3. Forskolin (10 microM), an adenylyl cyclase activator, Sp-cAMPS (500 microM) and the catalytic subunit of protein kinase A increased glibenclamide-sensitive K+ currents 2.1-, 3.3- and 8.2-fold, respectively. 4. Nitric oxide and nitroprusside did not activate glibenclamide-sensitive K+ currents. 5. Dialysis of the cell's interior with inhibitors of protein kinase A (synthetic peptide inhibitor, 4.6 microM or H-8, 100 microM) completely blocked activation of K+ currents by CGRP. 6. Our results suggest the following signal transduction scheme for activation of K+ currents by CGRP in arterial smooth muscle: (1) CGRP stimulates adenylyl cyclase, which leads to an elevation of cAMP; (2) cAMP activates protein kinase A, which opens ATP-sensitive K+ channels.
Quayle
J M
JM
Department of Pharmacology, University of Vermont, Colchester 05446-2500.
Bonev
A D
AD
Brayden
J E
JE
Nelson
M T
MT
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001711:Biotransformation / Q000187:drug effects; D015740:Calcitonin Gene-Related Peptide / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D004594:Electrophysiology; D004789:Enzyme Activation / Q000502:physiology; D005905:Glyburide / Q000494:pharmacology; D066298:In Vitro Techniques; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects*; D011817:Rabbits; D015398:Signal Transduction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D015221:Potassium Channels; D005576:Colforsin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D015740:Calcitonin Gene-Related Peptide; D005905:Glyburide; D002118:Calcium