The binding of calcium ion by the human erythrocyte membrane

ATP-independent calcium net movements in human red cell ghosts

“…The bound Ca could not be removed from these sites by washing the cells in EDTA-containing isotonic solution but was largely removed by washing in hypotonic solution. In white erythrocyte membranes the equilibrium between membranes and medium is established within 10 man, EDTA reduces the binding markedly and diminishing the ionic strength increases the amount of membrane-bound Ca (Gent, Trounce &Walser, 1964;Long & Mouat, 1971;Forstner & Manery, 1971). The conclusion seems reasonable that type "A" binding sites are located in the depth of the membrane, separated from the medium by diffusion barriers to Ca, whereas in high-permeability-ghosts the Ca binding sites are freely accessible to external Ca and EDTA.…”

Dependence on calcium concentration and stoichiometry of the calcium pump in human red cells

“…Ca (1 /%mole/l. cells) will to a large extent be membrane bound, considering the binding properties found by Gent et al (1964) mentioned above. If, for the argument's sake, an increase in cellular Ca2+ concentration by a factor as small as 2 is postulated for the effect on K permeability seen by Lew (1970), it follows that the resting Ca2+ concentration is below 10-6 M, which is in agreement with the present contention.…”

Ca binding to the human red cell membrane: Characterization of membrane preparations and binding sites

“…Previous studies of Ca binding to the human red cell membrane have shown that, in both intact cells and ghosts, Ca binding is apparently due to a metabolically independent electrostatic adsorption to anionic membrane sites (Gent, Trounce & Walser, 1964;Seaman, Vassar & Kendall, 1969;Forstner & Manery, 1971;Long & Mouat, 1971).…”