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Ionic permeabilities of rat renal cortical brush-border membrane vesicles
The American Journal of Physiology
|April 1, 1987
Summary
Electrolytes do not readily equilibrate across renal cortical brush-border membrane vesicles (BBMV). Studies show a sustained electrolyte gradient, impacting data interpretation in kidney research.
Area of Science:
- Nephrology
- Membrane Biophysics
- Cell Physiology
Background:
- Renal cortical brush-border membrane vesicles (BBMV) are crucial for studying kidney transport.
- Previous studies assumed rapid electrolyte equilibration across BBMV.
Purpose of the Study:
- To investigate electrolyte equilibration across rat BBMV prepared using different methods.
- To assess the impact of preparation techniques on BBMV properties and electrolyte gradients.
Main Methods:
- Utilized rat BBMV prepared via free-flow electrophoresis (FFE), Mg aggregation, and Ca aggregation.
- Employed a fluorescent probe (diS-C3-(5)) to measure intravesicular ion concentrations and membrane potential.
- Assessed Na-dependent glucose uptake to approximate intravesicular KCl concentration.
Main Results:
- KCl failed to reach electrochemical equilibrium in BBMV across all preparation methods, even after prolonged incubation.
- A significant inwardly directed electrolyte gradient was consistently observed.
- Intravesicular electrolyte concentration and chloride to potassium conductance (GCl/GK) varied with preparation method (FFE vs. Mg/Ca aggregation).
Conclusions:
- The assumption of ready electrolyte equilibration across BBMV is incorrect.
- BBMV preparation methods influence intravesicular electrolyte concentrations and membrane conductance.
- The apparent impermeance of BBMV necessitates careful consideration when interpreting experimental data related to intravesicular electrolyte concentrations.