Submitted to: Nutrition Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2006
Publication Date: 3/1/2006
Citation: Phillippy, B.Q. 2006. TRANSPORT OF CALCIUM ACROSS CACO-2 CELLS IN THE PRESENCE OF INOSITOL HEXAKISPHOSPHATE. Nutrition Research. 26(3):146-149. Interpretive Summary: Phytic acid is a phosphate compound that is present in large amounts in seeds and reduces the bioavailability of minerals. Cell culture was used to determine the effect of various combinations of phytate and calcium on the absorption of calcium. Low concentrations of phytate had no effect, whereas high concentrations inhibited the transport of calcium through the Caco-2 cells. However, increasing concentrations of calcium resulted in increased calcium absorption at all phytate concentrations. This implied that the inhibitory effect of phytate in foods and feeds may be overcome by increasing the amount of calcium in the diet.
Technical Abstract: The Caco-2 enterocyte cell model was used to determine whether low concentrations of inositol hexakisphosphate (InsP6, phytate) may enhance calcium absorption as was recently reported for several other types of mammalian cells. Three week-old Caco-2 cell layers grown in tissue culture plates with or without cell culture inserts were incubated with [45Ca]Cl2 to examine calcium transport or uptake, respectively. No increases in calcium uptake were observed in the presence of micromolar levels of InsP6, whereas millimolar levels of InsP6 gave incongruous results depending on the calcium concentration. The fractional apical to basolateral calcium transport was significantly inhibited (P<0.05) by InsP6 levels of 100 µM and above, but the total molar amount of calcium transported still increased with increasing concentrations of calcium. It was concluded that Caco-2 cells transport is a better indicator of calcium availability than uptake, and higher consumption of calcium may overcome the inhibition of InsP6.