Interactions of pH and ascorbate in intestinal iron absorption

Area of Science:

• Gastroenterology
• Nutritional Science
• Biochemistry

Background:

• In vivo animal models are common for studying iron absorption.
• Acidic solutions are typically used to administer iron experimentally.
• The impact of luminal pH changes on iron bioavailability is not fully understood.

Purpose of the Study:

• To investigate the effect of intestinal luminal pH changes on iron absorption in vivo.
• To determine the relationship between pH-dependent iron solubility and iron uptake.
• To assess the role of ascorbate in mitigating pH-induced inhibition of iron absorption.

Main Methods:

• Monitoring pH changes in rat intestinal segments after administering acidic iron solutions.
• Quantifying mucosal iron uptake over time in iron-deficient rats.
• Assessing iron solubility and binding characteristics in intestinal fluid with and without ascorbate.

Main Results:

• Luminal pH increased from acidic levels to pH 6.8 within 15 minutes of iron solution administration.
• Iron uptake ceased by 5 minutes, coinciding with the pH rise above 4.
• Ascorbate addition prevented iron uptake cessation despite the pH increase.
• Iron precipitated in fasted rat intestinal fluid but a fraction remained bound to high molecular weight components, available to desferrioxamine B.

Conclusions:

• Intestinal pH significantly impacts iron bioavailability by altering iron solubility.
• The cessation of iron absorption is linked to pH-induced iron precipitation.
• Ascorbate enhances iron absorption by maintaining iron solubility, even with rising pH.