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. 2004 Oct 22;88(1):715–738. doi: 10.1529/biophysj.104.045633

FIGURE 3.

FIGURE 3

Passive and active transport of amprenavir across the monolayer of confluent MDCK cells is shown by nmol in the receiver chamber over 6 h when the donor side begins with 90 μM amprenavir. The solid symbols show passive permeability across the cell monolayer when the basolateral chamber was the donor side B > A (♦) and when the apical side was the donor A > B (•). The active transport by P-gp was completely inhibited by preincubation with 2 μM GF120918 added to both chambers. The open symbols show the effect of P-gp on transport of amprenavir across the cell monolayer, which occurs in the absence of GF120918. The fact that the activation of transport in the B > A direction (⋄) over the passive transport by P-gp, indicated by the up arrow, is greater than the inhibition in the A > B direction (O), indicated by the down arrow, proves that there are only two kinetic barriers to transport, as explained in the text.