Effects of calcium and sugars on intestinal manganese absorption.

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.