Inositol phosphates inhibit uptake and transport of iron and zinc by a human intestinal cell line.
To examine the influence of inositol phosphates on the uptake and absorption of Fe and Zn, Caco-2 cells were grown on either plastic (uptake studies) or porous membranes in bicameral chambers (transport/absorption studies). Caco-2, a human colon adenocarcinoma cell line, was selected as the test cell because it spontaneously differentiates into polarized enterocyte-like cells at confluency. Uptake of Fe (added as Fe-nitrilotriacetate complex) from a calcium-free solution by fully differentiated cells was 37 pmol/cm2. Addition of 10-fold molar excess of individual inositol phosphates (IP3, IP4, IP5 or IP6) decreased Fe solubility by 13 to 25% and reduced Fe uptake by 50 to 65%. The rate of transport of Fe from the apical solution into the basolateral chamber [1.4 +/- 0.1 pmol/(h.cm2)] decreased (34-96%) in proportion to the degree of phosphorylation of the inositol derivative in the apical compartment. Uptake and transepithelial transport of Zn were 246 +/- 5 pmol/cm2 and 23 +/- 1 pmol/(h.cm2), respectively. The solubility, uptake and rate of transport of Zn also decreased in proportion to the degree of phosphorylation of inositol. These results demonstrate the inhibitory influence of IP3-IP6 on the uptake and transport of Fe and Zn and support the usefulness of the Caco-2 human cell line as an appropriate model for evaluating the effects of specific dietary factors on trace metal bioavailability.
Han
O
O
Department of Food, Nutrition and Food Service Management, University of North Carolina, Greensboro 27412.
Failla
M L
ML
Hill
A D
AD
Morris
E R
ER
Smith
J C
JC
D003110:Colonic Neoplasms; D006801:Humans; D007295:Inositol Phosphates / Q000494:pharmacology*; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D007501:Iron / Q000378:metabolism*; D007700:Kinetics; D010766:Phosphorylation; D012995:Solubility; D014407:Tumor Cells, Cultured; D015032:Zinc / Q000378:metabolism*
D007295:Inositol Phosphates; D007501:Iron; D015032:Zinc