AJP - Cell Physiology, Vol 235, Issue 5 159-C167, Copyright © 1978 by American Physiological Society
Na-K pump and Na-K-ATPase: disparity of their temperature sensitivity
J. S. Willis, J. C. Ellory and J. H. Becker
As previously observed in red blood cells, ouabain-sensitive K influx of
kidney cells grown in culture for 3 days was much less inhibited by cooling
that Na-K-ATPase of the same cells. (At 5 degrees C K influx was 9.7% of
that at 38 degrees C, Na-K-ATPase, 1--2%.) Resealed ghosts of erythrocytes
of ground squirrels were made containing 24Na and ATP, and the Na efflux
and ATP hydrolysis were measured simultaneously. Under these conditions
there was no difference in the reduction of activity with cooling, and the
amount of reduction was close to that of active K transport in intact
cells. The high sensitivity to temperature, characteristic of broken
membranes, could not be induced in intact cells or resealed ghosts by
eliminating either the Na/K gradient or the ATP gradient nor by chelation
of cellular and extracellular Ca. It could not be eliminated in broken
membranes by protection with ATP or Mg. Structural reorganization of
membrane during lysis may cause the increase in temperature sensitivity of
Na-K-ATPase.
