TABLE 1

IC50 values for OATP1B1-mediated uptake of [3H]E2G, [3H]E1S, and [3H]BSP

OATP1B1-mediated uptake of [3H]E2G (0.1 µM, 5 min), [3H]E1S (0.01 µM, 1 min), and [3H]BSP (0.01 µM, 5 min) was examined in the presence and absence of inhibitors as shown in Fig. 2. IC50 values were estimated by nonlinear regression analysis based on Eq. 1 or 2 under Materials and Methods, and are presented as mean ± S.D.

InhibitorsSubstrates
[3H]E2G[3H]E1S[3H]BSP
IC50 (or Km) µM
E1S0.095 ± 0.0150.271 ± 0.013b0.429 ± 0.175a
611 ± 387a
CsA0.118 ± 0.0150.732 ± 0.2240.694 ± 0.149
BSP0.131 ± 0.0100.215 ± 0.0580.327 ± 0.033b
Ritonavir0.397 ± 0.02346.4 ± 9.83.38 ± 0.66
Rifampin0.585 ± 0.0746.96 ± 1.312.75 ± 0.62
Tacrolimus0.668 ± 0.1561.78 ± 0.343.57 ± 0.43
Erythromycin4.88 ± 0.6513.4 ± 4.063.3 ± 11.5
E2G7.04 ± 0.53b16.6 ± 2.439.3 ± 9.0
Ketoconazole9.90 ± 2.4015.4 ± 3.760.9 ± 26.1
TCA19.0 ± 1.050.0 ± 4.8161 ± 35
Verapamil22.3 ± 4.244.0 ± 7.384.3 ± 30.1
Gemfibrozil26.4 ± 2.1381 ± 60173 ± 34
Probenecid79.4 ± 5.8227 ± 69740 ± 181
  • a E1S showed biphasic inhibition of [3H]BSP uptake, and the IC50 values for high- and low-affinity components are presented.

  • b Km values.