Interrelationship of Iron and Manganese Metabolism ∗

Abstract

A relationship between iron and manganese metabolism has been suggested by the observation of the incorporation of manganese into the porphyrin molecule of red cells and the increased gastrointestinal absorption of manganese in iron deficiency (1, 2). The present studies were performed to determine variations in the metabolism of each of these elements induced by deficiency or overload of the other.

Methods. Male albino rats (Wistar strain) weighing 200-250 g were used. The animals were fed a standard rat diet (General Biochemicals, Chagrin Falls, Ohio) except that the iron and manganese content was modified from test to test as stated. Iron absorption was measured following a test dose of 0.5 _μCi of ferrous-⁵⁹ Fe citrate per 0.25 mg of ferrous sulfate per 0.5 ml of distilled water, administered through a 17-gauge endoesophageal tube to rats fasted for 16 hr. Whole body radioactivity (0.8 MeV —→ ∞) was measured in a small-animal, whole-body liquid scintillation detector (Packard Armac, LaGrange, Illinois), 3 hr and 7 days after dosing to determine the percentage of the test dose absorbed by the rats.

An isolated intestinal loop technique was utilized to measure manganese absorption because of the significant hepatobiliary excretion of this element. The rat was anesthetized with sodium pentobarbital and the peritoneal cavity was exposed through a midline incision. A 6-cm closed loop of small intestine just distal to the ligament of Treitz was isolated with umbilical tape. One-half μCi of ⁵⁴Mn per 1.0 mg of MnCl₂ in 0.5 ml of saline was injected into the lumen of the loop and the abdominal wall was sutured together. One hr after the injection the animal was placed in the counter and the total radioactivity was measured.