Interrelation of intestinal transport system for manganese and iron.

Abstract

Abstract Open-ended loops of rat duodenum, jejunum, and ileum were perfused with labelled solutions containing 5 mM. of manganese (Mn). In iron overload (FeL), similar amounts of Mn were absorbed from the 3 sites, but in iron deficiency (FeD) Mn absorption was increased from both the duodenum and jejunum. When the proximal intestine was perfused for 5 to 90 minutes with 5 mM. Mn, absorption occurred at a constant rate in FeL, and at an increased but constant rate in FeD. In FeL absorption was closely dependent upon doses of 0.25 to 10 mM. Mn; in FeD, a greater proportion of the test dose was absorbed from the smaller than from the larger doses. In FeD, the addition of 5 mM. iron (Fe) to the Mn perfusate competitively inhibited Mn absorption; conversely Mn reduced Fe absorption. Greater amounts of Fe than Mn were absorbed from an equimolar mixture. In FeL, neither metal affected the absorption of the other except when given in large doses. The results suggest that in Fe 2 Mn is absorbed largely by diffusion, whereas in FeD, Mn absorption in the proximal intestine is increased by the enhanced activity of a system which is dose-saturable and can be competitively inhibited by Fe. Duodenal perfusion of Mn in patients with varying iron stores confirmed that the rate of absorption was increased in FeD and that the enhanced absorption can be inhibited by Fe. Measurements of Mn 54 excretion 10 days after an oral dose showed no difference between control and FeD patients indicating that the increased Mn absorbed in FeD is not retained in the body.