Mechanism underlying the inhibitory effect of high calcium carbonate intake on iron bioavailability from ferrous sulphate in anaemic rats

Abstract

The influence of high CaCO, intake on the bioavailability of Fe from FeSO, was assessed during Fe repletion of rats with Fe-deficiency-induced anaemia. Fe-deficient rats with a mean blood haemoglobin concentration of 4.1 mmol/l were fed on purified Fe-adequate diets containing either 6.2 or 25.0 g CaCO,/kg (ten rats per group). Haemoglobin repletion after 14 d was significantly depressed by high CaCO, intake (9.5 v. 9.8 mmol/l for high and low CaCO, intake respectively; P = 0.03), as was apparent Fe retention (367 v. 552 pg/d during days S7, P < 0.001 ; 146 Y. 1% pg/d during days 19-21, P < 0.001). The concentration of Fe in the liquid phase of the proximal half of the small intestine was significantly lower in the high-CaCO, group (3.71 v. 520 pg/g digesta; P = 0-02). Mucosal uptake and mucosal transfer of Fe were determined with orally administered %Fe and Cr as a non-absorbable marker. Mucosal transfer was significantly diminished by CaCO, loading (90 v. 100% of mucosal uptake; P = OM), whereas mucosal uptake was not. 59Fe retention values at 14 d after administration were not significantly different (57.6 v. 51.9%; P = 0.14).

A comparative study of iron retention in mynahs, doves and rats

“…Twelve 3-month-old male conventional Wistar rats (U: WU) were obtained from the Central Animal Facility of Utrecht University. This age group was chosen to be comparable with results published previously (Wienk et al, 1996). The doves and mynahs were kept in wire-mesh cages (1 ´0.6 ´1 m 3 ) as six birds per cage.…”

“…The doses of radiolabelled tracers were based on earlier studies in rats and birds, which demonstrated that 59 Fe was a good marker for following the absorption of iron (Ward et al, 1991;Cork et al, 1995;Wienk et al, 1996;Santos et al, 1997). Chromium ( 51 Cr) was chosen as the non-absorbable marker because it is not absorbed from the intestinal lumen (Hudson et al, 1971;Stevens, 1988) and it has the same transit time as iron (Marx, 1979;Wienk et al, 1996).…”

“…Chromium ( 51 Cr) was chosen as the non-absorbable marker because it is not absorbed from the intestinal lumen (Hudson et al, 1971;Stevens, 1988) and it has the same transit time as iron (Marx, 1979;Wienk et al, 1996).…”

“…The 51 Cr values were corrected for the Compton scatter attribute of 5 9 Fe. All values were corrected for radioisotope decay and for background counts after every measurement (Wienk et al, 1996).…”

“…We used the technique of whole-body counting of radioactivity after the oral administration of 59 Fe and 51 Cr, which enabled us to measure mucosal uptake, transfer, and retention of iron (Marx, 1979;Wienk et al, 1996). Two diets with different iron content were fed to the animals and the mynahs were compared with doves, a bird species not susceptible to dietary iron overload.…”