Is the red cell calcium pump electrogenic??

4. ROSSI J.P.F.C. Y SCHATZMANN, H.J

THE JOURNAL OF PHYSIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 1982 vol. 327 p. 1 - 15

0022-3751

1. In inside-out vesicles of high potassium permeability, prepared from human redcell membranes, volume changes accompanying the action of the Ca2+ pump weremeasured by recording the intensity of light scattered by a suspension of thesevesicles. Replacing Cl- by the impermeant gluconate anion changed swelling intoshrinking.2. Assuming that in Cl- media two Cl- ions accompany one Ca2+ ion moved bythe pump and in gluconate media two K+ ions are exchanged for one Ca2+ ion resultedin a good agreement between relative Ca2+ transport rate obtained from the volumechange 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- intocounter-transport ofCa2+ for K+ rules out that within the pump there is an obligatorycoupling of Ca2+ movement with movement of another ion species (including theproton). The conclusion, therefore, is that the Ca2+ pump must be electrogenic.4. The combination of measurement of volume change with direct measurement of45Ca movement yielded 56 #sl./mg protein for the volume of the vesicles.