AJP - Renal Physiology, Vol 252, Issue 5 838-F843, Copyright © 1987 by American Physiological Society
Na+-K+-ATPase activity in medullary thick ascending limb during short-term anoxia
M. E. Chamberlin and L. J. Mandel
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.
