Effect of NSAS and DAPP on Rhodamine 123 uptake in Caco-2 cells. Cells were exposed for 24 h to media alone (control), or to increasing concentrations of NSAS (A) or DAPP (B). Cellular accumulation of Rhodamine 123 was normalized with respect to the protein content in each well. Data is presented as mean ± standard deviation with N = 6. *p < 0.001 vs. control (A) and *p < 0.05 vs. control (B).