THE ACTIVATION OF THE CALCIUM PUMP OF HUMAN ERYTHROCYTE GHOSTS BY EXTERNAL SODIUM OR POTASSIUM

Publisher Summary This chapter discusses the activation of the calcium pump of human erythrocyte ghosts by external sodium or potassium. It discusses the influence of Na or K on active Ca extrusion from human erythrocyte ghosts, which have been resealed to both mono and divalent cations. Ghosts prepared in the presence of dextran are loaded with equimolar amounts of Mg and ATP and various free Ca concentrations buffered with EGTA. Isotonicity is restored with KCl and resealing is accomplished by either of the following two methods. The samples of the ghost suspension are withdrawn at 30–60 sec intervals and are rapidly squirted into a similar volume of an ice-cold isotonic choline-medium to which 2 mM LaCl 3 is added. After this, the ghosts are centrifuged through a cushion of n-dibutyl phthalate and analyzed for Ca by atomic absorption. The Na and K content of ghosts are also analyzed to assess the degree of resealing to monovalent cations.