Portal de Periódicos da CAPES

Is the red cell calcium pump electrogenic?

1982; Wiley; Volume: 327; Issue: 1 Linguagem: Inglês

10.1113/jphysiol.1982.sp014215

1469-7793

Juan Pablo F.C. Rossi, H. J. Schatzmann,

Lipid Membrane Structure and Behavior

1. In inside‐out vesicles of high potassium permeability, prepared from human red cell membranes, volume changes accompanying the action of the Ca2+ pump were measured by recording the intensity of light scattered by a suspension of these vesicles. Replacing Cl‐ by the impermeant gluconate anion changed swelling into shrinking. 2. Assuming that in Cl‐ media two Cl‐ ions accompany one Ca+ ion moved by the pump and in gluconate media two K+ ions are exchanged for one Ca2+ ion resulted in a good agreement between relative Ca2+ transport rate obtained from the volume change and from direct measurement of 45Ca uptake in the two media. 3. The fact that it is possible to change co‐transport of Ca with Cl‐ into counter‐transport of Ca2+ for K+ rules out that within the pump there is an obligatory coupling of Ca2+ movement with movement of another ion species (including the proton). The conclusion, therefore, is that the Ca2+ pump must be electrogenic. 4. The combination of measurement of volume change with direct measurement of 45Ca movement yielded 5‐6 microliter/mg protein for the volume of the vesicles.