Phospholipid-cholesterol membrane model. I. Correlation of resistance with ion content. II. Cation exchange properties. III. Effect of ca on salt permeability. IV. Ca-K uptake by sonically fragmented erythrocyte ghosts
✍ Scribed by Mikulecky, Donald C. ;Tobias, Julian M.
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1964
- Tongue
- English
- Weight
- 868 KB
- Volume
- 64
- Category
- Article
- ISSN
- 0095-9898
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✦ Synopsis
A phospholipidcholesterol membrane model has recently been described whose electrical conductance, water content and water permeability can reversibly be lowered by CaCL or increased by KC1 (Tobias et al., '62; Leitch et al., '64). These properties mimic certain cell behavior often attributed to the plasma membrane. They also suggest that the model, and by analogy, the cell membrane, might be cation exchangers. The following experiments were done to evaluate this possibility for the model and for fragments of human erythrocyte ghosts. It will be seen that the model is a cation exchanger: The ion distribution between membrane and solution can be described by a Donnan equilibrium or by the formation of a weak salt of fixed anion and counter cation. Resistance, previously shown to be modified by externally applied salt solutions, is now seen to depend on the amounts of Ca and K actually in the membrane, and permeability to NaCl and to KC1 is found to be decreased in the presence of Ca. Evidence is also presented that fragments of red blood cell ghosts exhibit ion uptake and Ca dependent water uptake qualitatively comparable to that of the model. This lends strength to the hypothesis that the model is a partial representation of the cell surface and that certain erythrocyte membrane components do in fact behave as ion exchangers.
Methods
Phospholipidcholesterol membranes were made by impregnating Millipore filter