Factors affecting the microclimate pH in rat jejunum.

Area of Science:

• Gastroenterology
• Physiology
• Biochemistry

Background:

• The intestinal surface exhibits a microclimate pH distinct from the bulk luminal contents.
• Understanding this pH gradient is vital for comprehending nutrient absorption and intestinal function.

Purpose of the Study:

• To investigate the factors influencing the pH microclimate at the rat jejunum surface.
• To elucidate the roles of sodium-hydrogen (Na+-H+) antiport, mucus, and nutrient transport in regulating jejunal surface pH.

Main Methods:

• Utilized single-barrelled pH-sensitive microelectrodes for in vitro measurements of rat jejunum surface pH.
• Manipulated perfusion solutions (varying Na+ concentration, glucose, amiloride) and surface mucus to assess pH gradient changes.

Main Results:

• A significant pH gradient (luminal pH 7.30 to 6.05) was observed in the jejunal microclimate.
• Na+-H+ antiport activity and the mucus layer were essential for maintaining the acidic microclimate.
• D-glucose enhanced acidity, while glycylglycine and L-carnosine reduced the pH gradient, indicating H+-dipeptide co-transport involvement.

Conclusions:

• The Na+-H+ antiport and mucus layer are critical for establishing and maintaining the jejunal microclimate pH gradient.
• H+-coupled co-transport mechanisms, including H+-dipeptide transport, significantly influence and reduce this pH gradient.