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Donnan equilibrium and pH gradient in isolated tracheal apical membrane vesicles
The American Journal of Physiology
|November 1, 1985
Summary
Bovine tracheal epithelial cells maintain electrical potential gradients (delta psi) and pH gradients (delta pH) across their apical membranes. These gradients are sensitive to ionic strength, suggesting a Donnan equilibrium mechanism.
Area of Science:
- Cell Biology
- Biophysics
- Epithelial Physiology
Background:
- Apical plasma membrane vesicles are crucial for studying epithelial transport.
- Understanding ion gradients is key to epithelial function.
Purpose of the Study:
- To characterize the electrical potential gradient (delta psi) and transmembrane pH gradient (delta pH) in bovine tracheal epithelial apical membrane vesicles.
- To investigate the influence of ionic strength on these gradients.
Main Methods:
- Isolation of apical plasma membrane vesicles from bovine tracheal epithelium.
- Measurement of delta psi using 86Rb+ distribution with valinomycin.
- Determination of delta pH using [14C]methylamine distribution.
Main Results:
- Maximal delta psi of -54.3 mV and delta pH of 0.75 units were observed under low ionic strength.
- Increasing ionic strength reduced both delta psi and delta pH.
- The delta pH varied in parallel with the delta psi.
Conclusions:
- The results suggest that both 86Rb+ and H+ are in a Donnan equilibrium.
- Impermeant negative charges within the vesicle interior likely influence these gradients.