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Effects of calcium and sugars on intestinal manganese absorption
T A Lutz1, A Schroff, E Scharrer
1Institute of Veterinary Physiology, University of Zürich, Switzerland.
Abstract:
An in vivo luminal perfusion technique was used to investigate the influence of Ca, Mg, lactose, and glucose on Mn absorption in different segments of the rat intestine. Mn absorption was determined by measuring disappearance of 54Mn activity from the perfusion solution containing 0.1 or 0.01 mmol/L Mn. Na and water absorption were also determined. Mn absorption decreased during the first 30 min of perfusion to reach a steady state thereafter. Ca (1 mmol/L) inhibited Mn absorption in the proximal jejunum and in the colon, whereas Mn absorption was increased by Ca in the distal jejunum. Mg (1 mmol/L), lactose, and glucose (25 mmol/L each) had no effect on Mn absorption in the jejunum. These results can be explained by a direct interaction of Mn and Ca during transcellular Ca transport in the proximal jejunum and colon. The reason for the stimulatory effect of Ca in the distal jejunum is unknown.
Insights
Calcium influences manganese (Mn) absorption differently across rat intestinal segments. While inhibiting Mn absorption in the proximal jejunum and colon, calcium stimulated it in the distal jejunum.
Area of Science:
- Gastroenterology
- Nutritional Science
- Mineral Metabolism
Background:
- Manganese (Mn) is an essential trace element crucial for various physiological processes.
- Understanding factors influencing Mn intestinal absorption is vital for nutritional and toxicological assessments.
- Intestinal absorption of minerals can be modulated by luminal factors and segment-specific transport mechanisms.
Purpose of the Study:
- To investigate the impact of calcium (Ca), magnesium (Mg), lactose, and glucose on Mn absorption in distinct rat intestinal segments.
- To elucidate the interactions between Mn and other luminal substances during intestinal transit.
Main Methods:
- An in vivo luminal perfusion technique was employed in rats.
- Radioactive 54Mn was used to quantify Mn absorption rates in different intestinal segments.
- Sodium and water absorption were concurrently measured to assess overall intestinal function.
Main Results:
- Mn absorption exhibited an initial decrease followed by a steady state within 30 minutes of perfusion.
- Calcium (1 mmol/L) significantly inhibited Mn absorption in the proximal jejunum and colon.
- Conversely, calcium (1 mmol/L) enhanced Mn absorption in the distal jejunum, while Mg, lactose, and glucose showed no significant effects in the jejunum.
Conclusions:
- The findings suggest a complex, segment-specific interaction between calcium and manganese absorption in the rat intestine.
- A direct interaction between Mn and Ca during transcellular calcium transport may explain inhibition in the proximal jejunum and colon.
- The stimulatory effect of Ca on Mn absorption in the distal jejunum warrants further investigation.