title: Potassium-chloride cotransport in cultured chick heart cells.
abstract: The polystrand preparation of cultured chick heart cells has a unidirectional transmembrane Cl- efflux that is twice K+ efflux. However, Cl- conductance of this heart cell membrane is low [regardless of extracellular K+ (K+o)], suggesting the existence of electroneutral Cl--dependent transport mechanisms. Furosemide (10(-3) M) decreases the 36Cl tracer efflux rate constant from a control value of 0.67 to 0.33 min-1. Extracellular Na+--free solution, which depletes intracellular Na+ within 1 min, has no significant effect on 36Cl efflux. K+o-free solution plus 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS; 10(-4) M) promotes the loss of Cl- against the Cl- electrochemical gradient; Cl- loss is furosemide sensitive in a dose-dependent manner. Incubating polystrands in 133 mM K+o, normal extracellular Cl- (Cl-o) solution causes net K+ and Cl- uptake in a 1:1 stoichiometry as well as a furosemide-sensitive volume increase; 130 mM extracellular choline or Li+ cannot mimic this high-K+o-induced volume increase. Removal of Cl-o from 133 mM K+o solution prevents K+ uptake and causes a Cl- loss as well as a furosemide-sensitive volume decrease. Adjusting Cl-o concentrations in high-K+o solution plus DIDS, so that the Cl- chemical gradient equally opposes the K+ chemical gradient, prevents high-K+o-induced volume changes. These data suggest that the cardiac cell membrane contains a furosemide-sensitive K+-Cl- cotransport mechanism.
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D002712:Chlorides / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D028021:Sodium-Potassium-Chloride Symporters; D005665:Furosemide; D011188:Potassium