title: Biochemical characterization of the Na+/K+/Cl- co-transport in chick cardiac cells.
abstract: Cultured chick cardiac cells possess a Na+K+Cl-co-transport system that is inhibited by the "loop diuretics" benzmetanide (IC50 = 0.3 microM), bumetanide (IC50 = 0.6 microM), piretanide (IC50 = 1.5 microM) and furosemide (IC50 = 5 microM). The K0.5 values for Cl- and Na+ activation of the bumetanide-sensitive 86Rb+ uptake are 59 mM and 40mM respectively. Bumetanide also inhibits a 22Na+ uptake component that is suppressed when external Cl- or K+ are substituted by impermeant ions. The ratio of bumetanide-sensitive 86Rb+ to 22Na+ uptake is close to 1. The cardiac Na+/K+/Cl- cotransport is a major uptake pathway for Na+ and K+. It accounts for 50% of the initial rate of 86Rb+ uptake and 17% of the initial rate of 22Na+ uptake by chick cardiac cells. It is activated two-fold by an hyperosmotic shock produced with 200 mM mannitol.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002642:Chick Embryo; D002712:Chlorides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D009206:Myocardium / Q000378:metabolism*; D009997:Osmotic Pressure; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
chemical_list: D002712:Chlorides; D002034:Bumetanide; D010042:Ouabain; D012964:Sodium; D012413:Rubidium; D011188:Potassium