Fitted Consensus Kinetic Values for MDCK-MDR1-NKI Confluent Cell Monolayers.

ak1 is the drug independent association rate constant from the membrane to P-gp. The average value from Agnani et al. [13] is shown. This value is fixed for all drugs fitted here.
bT(0) is the surface density of efflux active P-gp in the apical membrane inner monolayer for all drugs. The average value from Agnani et al. [13] is shown. This value is fixed for all drugs fitted here. The units P-gp/µm2 can be converted to µmols P-gp per liter of inner apical membrane simply by dividing by 0.8, e.g. 800 P-gp/µm2 is equal to 1×10−3 M P-gp in the inner apical leaflet [21].
ckr is the dissociation rate constant from the P-gp binding site into the apical bilayer.
dk2 is the efflux rate constant from the P-gp binding site into the apical chamber.
eKC = k1/kr is the substrate binding constant from inner apical membrane monolayer to P-gp.
fPBA and PAB refers to the lipid bilayer steady-state passive permeability coefficient, B>A and A>B respectively, measured +GF120918. kB and kA refers to the 1st order clearances for transport through bidirectional uptake transporters.
gIt was assumed that the partition coefficient was the same as CsA and that the permeability coefficients were 500 nm/s, since they could not be measured, due to the lack of radiolabelled GF120918. The chosen values will not have a significant effect upon the results with GF120918 as an inhibitor.