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Chloride transport across rat ileal basolateral membrane vesicles
1Department of Pediatric Gastroenterology and Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
Summary
This study reveals two chloride (Cl-) transport mechanisms in rat ileal basolateral membranes: an electrogenic process and a bumetanide-sensitive Na+/K+/2 Cl- cotransporter. Neither pH nor bicarbonate gradients influenced Cl- transport.
Area of Science:
- Physiology
- Molecular Biology
- Membrane Transport
Background:
- Chloride (Cl-) transport is crucial for intestinal function.
- Understanding basolateral membrane transport mechanisms is key to elucidating overall intestinal Cl- handling.
Purpose of the Study:
- To investigate the mechanisms of Cl- transport across the rat ileal basolateral membrane.
- To identify specific transporters and driving forces involved in Cl- uptake.
Main Methods:
- Preparation of rat ileal basolateral membrane vesicles.
- Utilized rapid filtration technique for Cl- uptake studies.
- Employed ion gradients, specific inhibitors (e.g., bumetanide, 4,4-Diisothiocyanostilbene-2,2-disulfonic acid), and ionophores (valinomycin) to probe transport mechanisms.
Main Results:
- Cl- uptake was stimulated by combined Na+ and K+ gradients and by an inside-positive membrane potential.
- Bumetanide significantly inhibited Cl- uptake, indicating a Na+/K+/2 Cl- cotransporter activity.
- No stimulation of Cl- transport was observed with pH or HCO3- gradients, nor with outwardly directed Na+ and HCO3- gradients.
Conclusions:
- Rat ileal basolateral membranes exhibit at least two distinct Cl- transport pathways.
- These pathways include an electrogenic diffusive process and a bumetanide-sensitive Na+/K+/2 Cl- cotransporter.
- Cl- transport is not mediated by pH or bicarbonate gradients at the basolateral membrane.