Comparison of the side-dependent effects of Na and K on orthophosphate-, UTP-, and ATP-promoted ouabain binding to reconstituted human red blood cell ghosts.

Abstract

Ouabain binding promoted by orthophosphate (Pi) and its inhibition by Na were due to inside Pi and inside Na. External K inhibited Pi-promoted ouabain binding and Nao decreased the effectiveness of Ko. Inside UTPi stimulated the rate of ouabain binding which can be antagonized by either Nai or Ko acting alone. The actions of Nai and Ko were different when ouabain binding was promoted by Pi and UTPi compared to inside ATPi. With ATPi, the ouabain binding rate was only affected when Nai and Ko were both present. Possible differences in the mechanism of action of K and Na on Pi- and UTP-promoted binding were discussed in the light of their sidedness of action.