AJP - Cell Physiology, Vol 263, Issue 5 C1057-C1064, Copyright © 1992 by American Physiological Society
Oxygenation-activated K fluxes in trout red blood cells
O. B. Nielsen, G. Lykkeboe and A. R. Cossins
Department of Zoophysiology, University of Aarhus, Denmark.
The effect of oxygenation on the dissipative fluxes of K in trout red blood
cells has been determined. Unidirectional influx under low oxygen tension
(PO2 = 1 kPa) was 0.56 +/- 0.07 mmol.l-1 packed cells.h-1. Within a few
minutes of equilibration with high oxygen tension (PO2 = 120 kPa), influx
was increased 14-fold, and this was associated with a progressive loss of
KCl and a cell shrinkage. K influx progressively declined over the
following 3 h to levels close to those characteristic of cells at low
oxygen tension. Replacement of medium Cl by NO3- or methane sulfonate
inhibited the stimulation due to high oxygen as did furosemide and low
extracellular pH. The oxygenation-stimulated influx was highly volume
sensitive, being increased by up to 100% by osmotic swelling and decreased
by osmotic shrinkage. By contrast, the small influx under low oxygen
tension was unaffected by either Cl replacement or by shrinkage and
increased only with extreme swelling. Thus high oxygen tension activated a
Cl-dependent and furosemide-sensitive K flux. Once activated, the mechanism
was rapidly deactivated on transfer back to low oxygen tension but slowly
deactivated when maintained at high PO2. The oxygenation-stimulated flux
mechanism promotes a rapid and more complete volume regulatory decrease
than in cells at low oxygen tension.
