Na+-K+-ATPase activity in medullary thick ascending limb during short-term anoxia.
Na+-K+-ATPase activity was measured in a suspension of rabbit medullary thick ascending limb tubules under oxygenated and anoxic conditions. Oxygenated, K-depleted tubules rapidly take up added extracellular potassium accompanied by a simultaneous increase in oxygen consumption. The ATP/O2 ratio was 12.5 +/- 0.7, suggesting a tight coupling between oxidative metabolism (6 ATP/O2) and Na+-K+-ATPase activity (2 K/ATP). On reaching anoxia, the tubules released potassium into the medium, but this rate was accelerated by the addition of ouabain, which indicated that the Na+-K+-ATPase was still operative in anoxia. Because 10 min of anoxia led to only a 15.7% decline in potassium content, a new steady state of potassium uptake and leakage must be reached during anoxia. Anaerobic metabolism maintained 73% of cellular ATP during 10 min of anoxia. Exposure of anoxic tubules to iodoacetate produced a 57% decline in ATP levels and a 33% decline in potassium content, which indicated that glycolysis is an important pathway in supplying energy during anaerobiosis.
D000208:Acute Disease; D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D005260:Female; D000860:Hypoxia / Q000201:enzymology*; D007679:Kidney Medulla / Q000201:enzymology* / Q000378:metabolism; D007684:Kidney Tubules / Q000201:enzymology*; D008138:Loop of Henle / Q000201:enzymology* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D000227:Adenine Nucleotides; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium