Fig. 4

Effects of treatment of Caco-2 cell monolayers with a basolateral supply of holo-Tf or an apical supply of ferric NTA on mRNA levels for iron transport genes. Values shown indicate relative mRNA levels for a TfR-1, b DMT-1 and c FPN in Caco-2 cells determined at day 21 post-seeding following incubation from day 14 to 21 of confluent Caco-2 cell monolayers established in bicameral chamber with medium containing metal-depleted FBS in the absence of any added iron (Control), presence of 10 μM ferric NTA added to the apical side of the cells only (10 μM FeNTA) or of 30 μM holo-Tf added to the basolateral side of the cells only (30 μM holo-Tf). Bars and error bars indicate mean + SD (n = 10 comprised of samples generated from 1 or 2 wells for each treatment from each of three separate plates set up in parallel with a total of five samples from each of two independent experiments). Data were compared either by Kruskal–Wallis test with Dunn’s multiple comparison post hoc test (for DMT-1 and TfR-1 where at least one data set did not pass the D’Agostino and Pearson’s omnibus normality test) or by one-way ANOVA with Tukey’s post hoc test (for FPN). Asterisks indicate statistically significant differences between treatments (*p < 0.05, **p < 0.01 and ***p < 0.001)