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Proton pathways in rat renal brush-border and basolateral membranes
Biochimica Et Biophysica Acta
|October 12, 1983
Summary
This study monitored pH gradients in rat kidney vesicles using acridine orange fluorescence. Findings reveal the Na+-H+ exchanger is primarily on the luminal membrane, crucial for bicarbonate reabsorption.
Area of Science:
- Renal Physiology
- Membrane Transport
- Biochemistry
Background:
- Understanding pH regulation in kidney tubules is vital for processes like bicarbonate reabsorption.
- Brush-border and basolateral membranes have distinct transport mechanisms that require characterization.
Purpose of the Study:
- To investigate the mechanisms of pH gradient formation and dissipation in rat kidney brush-border and basolateral membrane vesicles.
- To identify and characterize ion transport systems, specifically Na+-H+ exchange and conductances, in these membrane preparations.
Main Methods:
- Utilized acridine orange fluorescence quenching to monitor transmembrane pH gradients (delta pH).
- Isolated brush-border membrane vesicles (BBMVs) and basolateral membrane vesicles (BLMVs) from rat kidney cortex.
- Employed ion gradients (Na+, K+, Cl-, SO2-4) and specific inhibitors to probe transport activities.
Main Results:
- Acridine orange fluorescence accurately measured delta pH, independent of membrane potential.
- Brush-border membranes exhibit saturable Na+(Li+)-H+ exchange, partly via an electroneutral antiporter and partly via conductive pathways.
- Basolateral membranes show H+ and Cl- conductance but lack significant Na+-H+ exchange activity.
Conclusions:
- The electroneutral Na+-H+ exchanger is localized to the luminal (brush-border) membrane of kidney proximal tubule cells.
- This localization facilitates net proton secretion, essential for bicarbonate reabsorption in the mammalian kidney.
- Distinct transport properties of BBMVs and BLMVs underscore their specialized roles in renal function.