title: Mechanism underlying the inhibitory effect of high calcium carbonate intake on iron bioavailability from ferrous sulphate in anaemic rats.
abstract: The influence of high CaCO3 intake on the bioavailability of Fe from FeSO4 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 CaCO3/kg (ten rats per group). Haemoglobin repletion after 14 d was significantly depressed by high CaCO3 intake (9.5 v. 9.8 mmol/l for high and low CaCO3 intake respectively; P = 0.03), as was apparent Fe retention (367 v. 552 micrograms/d during days 5-7, P < 0.001; 146 v. 196 micrograms/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-CaCO3 group (3.71 v. 5.20 micrograms/g digesta; P = 0.02). Mucosal uptake and mucosal transfer of Fe were determined with orally administered 59Fe and Cr as a non-absorbable marker. Mucosal transfer was significantly diminished by CaCO3 loading (90 v. 100% of mucosal uptake; P = 0.04), 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). Fe contents of liver and spleen were significantly decreased by high compared with low CaCO3 intake (879 v. 590 micrograms Fe in liver, P < 0.001; 92 v. 63 micrograms Fe in spleen, P < 0.001). It is concluded that high intake of CaCO3 depresses Fe bioavailability in rats. The CaCO3-induced decrease in Fe solubility in the digesta probably was associated with an increased efficiency of mucosal Fe uptake so that the amount of mucosal uptake remained unaltered. The CaCO3-induced decrease in Fe transfer through the mucosal cytoplasm and/or basolateral membrane may have been responsible for the concurrent decrease in Fe bioavailability.
authors.affiliation: Department of Laboratory Animal Science, Utrecht University, Netherlands.
authors.forename: K J
authors.initials: KJ
authors.lastname: Wienk
authors.forename: J J
authors.initials: JJ
authors.lastname: Marx
authors.forename: A G
authors.initials: AG
authors.lastname: Lemmens
authors.forename: E J
authors.initials: EJ
authors.lastname: Brink
authors.forename: R
authors.initials: R
authors.lastname: Van Der Meer
authors.forename: A C
authors.initials: AC
authors.lastname: Beynen
mesh_terms: D018798:Anemia, Iron-Deficiency / Q000378:metabolism*; D000818:Animals; D002119:Calcium Carbonate / Q000494:pharmacology; D002136:Calcium, Dietary / Q000494:pharmacology*; D005243:Feces / Q000737:chemistry; D005296:Ferrous Compounds / Q000037:antagonists & inhibitors / Q000378:metabolism; D005766:Gastrointestinal Contents / Q000737:chemistry; D006454:Hemoglobins / Q000032:analysis; D007408:Intestinal Absorption; D007501:Iron / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008099:Liver / Q000737:chemistry; D008297:Male; D009753:Nutritive Value; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000737:chemistry
chemical_list: D002136:Calcium, Dietary; D005296:Ferrous Compounds; D006454:Hemoglobins; C020748:ferrous sulfate; D007501:Iron; D002119:Calcium Carbonate