A standing Na+ conductance in rat carotid body type I cells.
Substitution of extracellular Na+ with N-methyl D-glucamine caused marked hyperpolarisation in rat isolated carotid body type I cells, suggesting the presence of a standing Na+ conductance. Choline substitution produced smaller hyperpolarisations, whilst Li+ was virtually without effect. This Na+ conductance was not blocked by amiloride, tetrodotoxin, Zn2+ or Gd3+ and did not arise from electrogenic Na-glucose co-transport, since substitution of glucose with sucrose could not mimic the effects of Na+ substitution. Hypoxia and acidosis did not modify the tonic Na+ influx. Our results suggest that Na+ influx provides a constant depolarising influence on type I cells which acts to shift membrane potential beyond that required for initiation of neurosecretion, an essential step in carotid body chemotransduction.
Carpenter
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Institute for Cardiovascular Research, University of Leeds, UK.
Peers
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C
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000142:Acidosis, Respiratory / Q000503:physiopathology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002344:Carotid Body / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002794:Choline / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D006706:Homeostasis / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology; D008094:Lithium / Q000494:pharmacology; D008536:Meglumine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
D015221:Potassium Channels; D015222:Sodium Channels; D013779:Tetrodotoxin; D008536:Meglumine; D000584:Amiloride; D008094:Lithium; D012964:Sodium; D005682:Gadolinium; D015032:Zinc; D002794:Choline; D010100:Oxygen