Na+/H+ exchange mediates meal-stimulated ileal absorption

Area of Science:

• Gastroenterology
• Physiology
• Molecular Biology

Background:

• Meal ingestion enhances jejunoileal water and electrolyte absorption.
• Na(+)-glucose cotransport is implicated in meal-stimulated jejunal absorption.
• The role of Na+/H+ exchange in ileal absorption requires further investigation.

Purpose of the Study:

• To test the hypothesis that Na+/H+ exchange mediates basal and meal-stimulated ileal absorption.
• To elucidate the mechanisms of ileal water and electrolyte absorption following a meal.

Main Methods:

• Absorption studies were conducted on dogs with ileal Thiry-Vella fistulas.
• Luminal perfusion techniques were used to measure water, sodium, chloride, and glucose absorption.
• Amiloride was administered to inhibit Na+/H+ exchange, and glucose or mannitol were used to assess cotransport.

Main Results:

• Ileal absorption increased significantly post-meal, irrespective of luminal glucose or mannitol.
• Amiloride significantly reduced both basal and post-meal water and electrolyte absorption.
• Mannitol reduced basal absorption of water and electrolytes, suggesting a role for Na(+)-glucose cotransport.

Conclusions:

• Na+/H+ exchange and Na(+)-glucose cotransport contribute to basal ileal absorption.
• Na+/H+ exchange is the primary mediator of meal-stimulated ileal absorption.
• Na+/H+ exchange plays a crucial role in the physiological regulation of postprandial ileal absorption.