Dual modulation of swelling-activated chloride current by NO and NO donors in rabbit portal vein myocytes.
1. The effects of authentic NO and the NO donor S-nitroso-N-acetylpenicillamine (SNAP) on swelling-activated chloride currents (Iswell) were investigated in freshly dispersed rabbit portal vein smooth muscle cells. Iswell was recorded with the perforated patch configuration of the whole-cell patch clamp technique. 2. In approximately 50 % of cells NO and SNAP inhibited the amplitude of Iswell by about 45 % in a voltage-independent manner. Iswell was also inhibited by an inhibitor of NO-sensitive guanylate cyclase (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and by KT5823, an inhibitor of cGMP-dependent protein kinase. 3. In other cells both NO and SNAP enhanced Iswell by about 40 % in a voltage-independent manner. A similar increase was produced by application of the cell-permeable cGMP analogue 8-bromo-guanosine 3', 5'-cyclic monophosphate (8-Br-cGMP). However, 8-Br-cGMP had no effect on current amplitude in cells pre-treated with KT5823. In contrast 8-Br-cGMP increased the amplitude of Iswell in cells which had been pre-treated with ODQ. 4. SNAP also modulated Iswell recorded in the conventional whole-cell configuration with internal solutions containing 10 mM EGTA to rule out any contribution from Ca2+-activated Cl- currents. 5. These data suggest that the amplitude of Iswell can be enhanced by NO via a cGMP-dependent phosphorylation and inhibited by NO in a cGMP-independent manner.
Ellershaw
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DC
Department of Pharmacology and Clinical Pharmacology, Cardiovascular Research Group, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK.
Greenwood
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Large
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WA
D000818:Animals; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D008536:Meglumine / Q000378:metabolism / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000378:metabolism* / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011169:Portal Vein / Q000166:cytology / Q000378:metabolism*; D011817:Rabbits; D026423:S-Nitroso-N-Acetylpenicillamine; D012964:Sodium / Q000378:metabolism
D002614:Chelating Agents; D018118:Chloride Channels; D020030:Nitric Oxide Donors; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D008536:Meglumine; D026423:S-Nitroso-N-Acetylpenicillamine; D012964:Sodium; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D010396:Penicillamine; D006152:Cyclic GMP