FIG. 1.

Forward and reverse permeability of 10 μM digoxin (A) or 50 μM TFV (B) in the presence or absence of CsA through Caco-2 monolayers. The Pgp substrate digoxin, when incubated alone, had a reverse permeability 9.9-fold higher than its forward permeability (***, P < 0.001 by Student's unpaired two-tailed t test assuming equal variance), and a marked change in permeability was observed upon addition of CsA. No significant difference in TFV forward and reverse permeability or effect of CsA was observed (all P values, >0.05). Similar results for TFV were obtained when it was incubated at 5 μM (data not shown). Values represent the mean ± standard deviation from three independent studies done in duplicate.