Cation Transport and Structure of the Red-Cell Plasma Membrane

This paper recounts recent uwork concerning the Na aiid K permeability of red blood cells. The discussion deals principally with results derived from isolated red-cell membranes, or ghosts. Using defined isolation techniques, a system of ghosts is described in which Na is actively pumped. Like intact cells, the pump requires extracellular K and energy derived from the metabolism. The source of energy for the pump has been assessed by ineorporating normally impermeable substrates into the ghost interior at the tinle of hemolysis. The specific and direct substrate of the pump has been identified as ATP. Further studies are described that correlate the activity of the Na pump wvith an ATPase. This ATPase, like the pump, requires both Na and K for activity and is inhibited by cardiac glycosides. The evidence points toward the involvement of this ATPase as an intermediate componenit of the pump reaction.