title: Furosemide-sensitive potassium efflux in cultured mouse fibroblasts.
abstract: Transfer of LM(TK-) cells from normal growth medium to medium lacking K+ leads to a rapid loss of intracellular K+, which is 50-70% inhibited by furosemide or bumetanide. The diuretic-sensitive component of K+ efflux requires both Na+ and Cl-, and is presumably mediated by a K+, Na+, Cl- cotransport system of the kind described in avian erythrocytes and Ehrlich ascites cells. It can be calculated that such a system should be near equilibrium under normal growth conditions but should mediate net efflux (as observed) when the driving force is altered by reducing extracellular K+. The diuretic-sensitive component of net K+ efflux is also sensitive to amiloride. This effect is probably indirect, however, with amiloride acting to block the Na+ influx that supplies Na+ to the cotransport system. At the low extracellular K+ concentrations employed in these studies, the diuretic-sensitive system is a physiologically important pathway of K+ loss. The rate of growth in low-K+ medium can be increased (or the rate of cell lysis decreased) by adding diuretic or by reducing external Na+ or Cl-.
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002460:Cell Line; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology*; D008433:Mathematics; D051379:Mice; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013997:Time Factors
chemical_list: D002712:Chlorides; D002034:Bumetanide; D000584:Amiloride; D005665:Furosemide; D012964:Sodium; D011188:Potassium