ATP-sensitive K+ channel activation by calcitonin gene-related peptide and protein kinase A in pig coronary arterial smooth muscle.
1. We used patch clamp to study whole-cell K+ currents activated by calcitonin gene-related peptide (CGRP) in smooth muscle cells freshly dissociated from pig coronary arteries. 2. CGRP (50 nM) activated an inward current at -60 mV in symmetrical 140 mM K+ that was blocked by glibenclamide (10 microM), an inhibitor of ATP-sensitive potassium (KATP) channels. CGRP-induced currents were larger in cells dialysed with 0.1 mM ATP than with 3.0 mM ATP. 3. Forskolin (10 microM) activated a glibenclamide-sensitive current, as did intracellular dialysis with cAMP (100 microM). The catalytic subunit of cAMP-dependent protein kinase (protein kinase A, PKA), added to the pipette solution, activated equivalent currents in five out of twelve cells. 4. CGRP-induced currents were reduced by the PKA inhibitors adenosine 3',5'-cyclic monophosphorothioate, RP-isomer, triethylammonium salt (Rp-cAMPS; 100 microM) and N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulphonamide+ ++ dihydrochloride (H-89; 1 microM), and abolished by inclusion of a PKA inhibitor peptide in the pipette solution. 5. The beta-adrenergic agonist isoprenaline (10 microM) also activated a glibenclamide-sensitive K+ current. 6. CGRP-induced currents were unaffected by the inhibitor of cGMP-dependent protein kinase (PKG) KT5823 (1 microM). Sodium nitroprusside (10 microM) did not activate a glibenclamide-sensitive current in cells held at -60 mV, but did activate an outward current at +60 mV that was abolished by KT5823, or by 100 nM iberiotoxin (an inhibitor of BKCa channels). 7. Our findings suggest that CGRP activates coronary KATP channels through a pathway that involves adenylyl cyclase and PKA, but not PKG.
Wellman
G C
GC
Ion Channel Group, Department of Cell Physiology and Pharmacology, University of Leicester, PO Box 138, Leicester LE1 9HN, UK.
Quayle
J M
JM
Standen
N B
NB
D000255:Adenosine Triphosphate / Q000502:physiology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D003331:Coronary Vessels / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D004553:Electric Conductivity; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D013552:Swine
D000318:Adrenergic beta-Agonists; D004791:Enzyme Inhibitors; D015221:Potassium Channels; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D015740:Calcitonin Gene-Related Peptide; D007545:Isoproterenol