title: Role of L-type calcium channels and PKC in active tone development in rabbit coronary artery.
abstract: The present study investigated active tone development in isolated ring segments of rabbit epicardial coronary artery. Endothelium-denuded (E-) or endothelium-intact (E+) vessels treated with the NO synthase inhibitor N(omega)-nitro-L-arginine (100 microM) developed active tone, which was enhanced by stretch and reversed by the NO donor sodium nitroprusside (SNP; IC(50)=9 nM). Nifedipine abolished active tone and the contractile response to phorbol dibutyrate (PDBu; 10 nM) with the same potency (IC(50)=8 nM), whereas 300 nM PDBu responses were only partially blocked by nifedipine. The classical and novel PKC inhibitors GF-109203X (IC(50)=1-2 microM) and chelerythrine (IC(50)=4-5 microM) and the classical PKC inhibitor Gö-6976 (IC(50)=0.3-0.4 microM) blocked both active tone and 10 nM PDBu responses with similar potency. Active tone development was associated with depolarization of membrane potential (E(m)) and a shift to the left of the E(m)-vs.-contraction relationship determined by varying extracellular potassium. The depolarization and leftward shift were reversed by either chelerythrine (10 microM) or SNP (30 nM). PDBu (100-300 nM) increased peak L-type calcium channel (Ca(v)) currents in isolated coronary myocytes, and this effect was reversed by chelerythrine (1 microM) or Gö-6976 (200 nM). SNP (500 nM) reduced Ca(v) currents only in the presence of the PKA blocker 8-bromo-2'-O-monobutyryl-cAMPS, Rp isomer (10 microM). In conclusion, active tone development in coronary artery is suppressed by basal NO release and is dependent on both enhanced Ca(v) activity and classical PKC activity. Both E(m)-dependent and -independent processes contribute to contraction. Our results suggest that one E(m)-independent process is direct enhancement of Ca(v) current by PKC.
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada, Reno, Anderson Medical Science Bldg. MS 352, Reno, Nevada 89557, USA.
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Cobine
authors.forename: Brid P
authors.initials: BP
authors.lastname: Callaghan
authors.forename: Kathleen D
authors.initials: KD
authors.lastname: Keef
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D053119:Benzophenanthridines / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D008564:Membrane Potentials; D009543:Nifedipine / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D020110:Pinacidil / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011817:Rabbits; D014661:Vasoconstriction; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D053119:Benzophenanthridines; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002227:Carbazoles; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D020030:Nitric Oxide Donors; D047428:Protein Kinase Inhibitors; D014665:Vasodilator Agents; C081021:Go 6976; D009599:Nitroprusside; D019335:Nitroarginine; D009569:Nitric Oxide; D015240:Phorbol 12,13-Dibutyrate; D020110:Pinacidil; D000242:Cyclic AMP; C016299:chelerythrine; D019001:Nitric Oxide Synthase; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D009543:Nifedipine; C070515:bisindolylmaleimide I; D011188:Potassium