Bradykinin and vasopressin stimulate Na+-K+-Cl- cotransport in cultured endothelial cells

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Abstract
We have characterized a Na+-K+-Cl- cotransporter in vascular endothelial cells (EC) cultured from different blood vessels and species that is inhibited by the diuretics furosemide and bumetanide (50% inhibitory concentration for 86Rb influx approximately 20 microM and 0.5 microM, respectively). Inward 86Rb influx mediated via this pathway is greater than 86Rb influx transported by the Na+-K+ pump in cultured EC from bovine and pig aorta, bovine vena cava, and baboon cephalic vein but not in human umbilical or saphenous vein EC. External Na+ or Cl- -stimulated, ouabain-insensitive 86Rb influx is equal to furosemide or bumetanide-sensitive 86Rb influx. Ouabain-insensitive 22Na influx is also partially inhibited by these drugs and stimulated by increasing external K+ or Cl-. Net Na+ extrusion occurs via the Na+-K+-Cl- cotransporter in the absence of external K+, whereas net Na+ influx occurs at higher external K+ (greater than 1 mM). Maximal concentrations (100 nM) of bradykinin and vasopressin increase the initial rate of bumetanide-sensitive 86Rb influx by approximately 60 and 70% (50% effective concentration approximately 1 and 0.6 nM, respectively). Addition of either ethyleneglycol-bis(beta-aminotethylether)-N,N'-tetraacetic acid or LaCl3 (to block calcium influx) prevents bradykinin-stimulated 86Rb influx. When intracellular calcium is elevated using ionomycin (100 nM), a Ca2+ ionophore, bumetanide-sensitive 86Rb influx increases approximately twofold. In contrast, isoproterenol (100 microM) and forskolin (50 microM), adenylate cyclase stimulators, decrease furosemide-sensitive 86Rb influx.(ABSTRACT TRUNCATED AT 250 WORDS)