TABLE 1

Inhibition of OCT1 by CsA and other drugs with and without 30-minute preincubation in stably transfected human embryonic kidney cells

Data represent the mean ± S.D. The IC50 values were estimated by Phoenix as indicated in Materials and Methods. [14C]Metformin (2 µM) was used as a probe substrate. Therefore, the IC50 values are considered as Ki (assuming competitive inhibition) because the ratio of metformin concentration to Km is small (<0.2).

DrugIC50IC50 Fold Shift
Without 30-Minute PreincubationWith 30-Minute Preincubation
µMµM
Cyclosporine A21.6 ± 4.50.43 ± 0.1250.2
Quinidine7.7 ± 0.94.5 ± 0.71.7
Pyrimethamine1.8 ± 0.21.3 ± 0.11.4
Ritonavir2.2 ± 0.31.1 ± 0.12.0
Trimethoprim9.6 ± 1.29.2 ± 0.71.1