(Na + K + 2Cl) cotransport in cultured embryonic chick heart cells.
The coupled movements of Na, K, and Cl were studied in cultured chick embryonic heart cells using ion-selective microelectrodes. Movements of K and Cl in response to changes in extracellular [K] ([K]o) showed a furosemide-sensitive coupled process. The movement of Na was then studied. Lowering extracellular [Na] ([Na]o) to 27 mM caused a decrease in intracellular Cl activity (aicl). Upon restoring [Na]o to 143 mM, Cl was taken up against its electrochemical gradient (delta mu Cl). In Cl-free solution, cells lost Na against delta mu Na and simultaneously lost Cl. Upon restoring extracellular [Cl] ([Cl]o), Cl was taken up against delta mu Cl; this was accompanied by an uptake of Na. The Cl uptake was 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS)-insensitive (0.1 mM) but inhibited by removing Nao. Both Cl and Na uptakes were potentiated by raising [K]o from 5.4 to 15 mM, and Na uptake was diminished by lowering [K]o to 1 mM. In all experiments, Cl and Na movements were furosemide (0.3 mM) or bumetanide-sensitive (0.1 mM). Removal of Nao, with resultant depletion of intracellular [Na] ([Na]i), blocked the furosemide or bumetanide-sensitive Cl loss or uptake upon exposure to zero or 133 mM [K]o + SITS (0.1 mM), respectively. These results suggest that cultured heart cells possess an electroneutral (Na + K + 2Cl) cotransport.
Liu
S
S
Department of Physiology, Duke University Medical Center, Durham, North Carolina 27710.
Jacob
R
R
Piwnica-Worms
D
D
Lieberman
M
M
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D002712:Chlorides / Q000378:metabolism* / Q000494:pharmacology; D004563:Electrochemistry; D005665:Furosemide / Q000494:pharmacology; D006321:Heart / Q000187:drug effects; D008839:Microelectrodes; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D002712:Chlorides; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D005665:Furosemide; D012964:Sodium; D011188:Potassium