Sodium transport in human intestinal basolateral membrane vesicles
Z Zamir1, J A Barry, K Ramaswamy
1Department of Medicine, Zablocki Veterans Administration Medical Center, Milwaukee, Wisconsin.
Gastroenterology
|December 1, 1992
Summary
Sodium (Na+) transport in human jejunum and ileum basolateral membrane vesicles occurs mainly via an Na+/H+ exchanger, with a minor conductive pathway also identified. This research clarifies intestinal ion transport mechanisms.
Area of Science:
- Gastroenterology
- Physiology
- Molecular Biology
Background:
- The basolateral membrane of intestinal cells plays a crucial role in nutrient and ion absorption.
- Understanding sodium (Na+) transport mechanisms is vital for comprehending intestinal function and fluid balance.
Purpose of the Study:
- To characterize the specific transport pathways for Na+ across the basolateral membrane vesicles (BLMV) of the human jejunum and ileum.
- To elucidate the kinetic properties and regulatory factors of Na+ transport in these intestinal segments.
Main Methods:
- Isolation of basolateral membrane vesicles (BLMV) from human jejunum and ileum organ donors.
- Utilizing an outward proton gradient to assess transport rates.
- Employing voltage-clamping techniques to differentiate conductive Na+ transport.
- Investigating the effects of amiloride, Li+, and NH4+ on Na+ uptake.
- Analyzing Na+ transport kinetics using saturation studies to determine Michaelis constant (Km) and Vmax values.
Main Results:
- An outward proton gradient significantly stimulated Na+ transport rates in both jejunal and ileal BLMV.
- Voltage-clamping revealed a minor conductive component of Na+ transport.
- Amiloride, Li+, and NH4+ demonstrated inhibitory effects on Na+ uptake, suggesting an Na+/H+ exchanger.
- Kinetic analysis indicated saturation kinetics with comparable Km and Vmax values between jejunum and ileum, with Vmax being significantly lower than reported for brush border membrane.
Conclusions:
- Na+ transport across the human jejunal and ileal basolateral membrane primarily occurs through an Na+/H+ exchanger.
- A minor conductive pathway contributes to Na+ transport in these tissues.
- The identified transport mechanisms are crucial for regulating Na+ homeostasis in the human intestine.
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