Further studies in rats on the influence of previous iron intake on the estimation of bioavailability of Fe

Abstract

1. Iron retention from 3 g wholewheat flour was measured in male Wistar rats previously given one high-Fe or control diet meal 12,24, 36,48 or 60 h before the test meal (Expt 1). The control diet was given at all other times. The procedure was then repeated in rats given one high- or low-Fe meal 12, 24, 36 or 48 h before the test meal (Expt 2). 2. There was a significant difference between groups given a high- or medium-Fe meal at 12,24,36 h (P < 0.001) and 48 h (P < 0.05) but not at 60 h. In the second experiment, there was a significant difference between groups given a high- or low-Fe meal at 12, 24 or 36 h but no difference when given the two diets 48 h before the test meal. The high-Fe meal depressed and the low-Fe meal enhanced subsequent 59 Fe retention: the effects were greatest at 12 h and diminished as the time interval between the high- or low-Fe meal and the test meal increased. The estimated mean time for the absorptive capacity of the mucosal cells to return to equilibrium was 54.0 (SEM 7.6) h. 3. Male Wistar rats were given high-, control or low-Fe diets for either 3 d or 28 d before an in vivo investigation in which the luminal loss of 59 Fe-labelled ferric citrate from duodenal and ileal loops was measured, and the proportional distribution between the carcass and the washed loop measured (Expt 3). 4. The luminal loss of 59 Fe-labelled ferric citrate was significantly affected by the previous diets (P < 0.001). Rats given a low-Fe diet absorbed more than those given a high-Fe diet but the period of time on the diet (3 or 28 d) had no effect on luminal loss. Significantly more 59 Fe was lost from duodenal than from ileal loops in all groups.