Influence of iron supplementation frequency on absorption efficiency and mucosal ferritin in anaemic rats

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Abstract
It is believed that frequent Fe doses decrease the efficiency of absorption as a consequence of the loading of intestinal mucosal cells with Fe from the previous supplemental dose. We examined this premise in thirty anaemic Sprague-Dawley rats given Fe supplements as FeSO4in 1 g preparations of a 50:50 (w/w mixture of low-Fe diet and sucrose under one of the following regimens: one 3 mg Fe dose daily for 3d, four 0.75mg doses daily at 6h intervals for 3d, and one 9mg dose on day 1 followed by two placebo (low-Fe diet) doses on days 2 and 3. All groups were fed on two low-Fe meals daily (8.3 mg Fe/kg diet). After an overnight fast rats were dosed with 1 ml of an59Fe-labelled ferric nitrilotriacetic acid solution (37 kBq59Fe, 50 μg Fe) orally and killed 10 h later. Absorption of59Fe was measured as the percentage of the59Fe retained by the carcass without the gastrointestinal tract 10 h after dosing relative to the initial59Fe dose. Haemoglobin-Fe gain, liver non-haem-Fe, and mucosal duodenal ferritin were determined after the 3 d supplementation period. Absorption of the test dose in rats supplemented once 3 d before assessment of Fe absorption was 2.6-fold greater than those supplemented with daily single doses and 1.9-fold greater than those supplemented with daily multiple doses. Our data indicate that both mucosal ferritin and liver Fe levels account for the higher absorption efficiency found in rats supplemented once to simulate intermittent regimens.