TABLE 1.
Functional characterization of stably transfected HEK-OATP1B1 and HEK-OATP2B1 cells and transiently transfected HEK-OATP1B3 cells for uptake of radiolabeled in vitro probe substratesa
| Substrateb | Transporter | Km (μM) | Vmax (pmol/min/mg protein) | CLint (μl/min/mg protein) | Reported Km (μM)c |
|---|---|---|---|---|---|
| [3H]ES | OATP1B1 | 2.3 | 28.0 | 12.17 | 2.4 (37), 12.5 (38) |
| [3H]ES | OATP2B1 | 5.8 | 32.0 | 6.4 | 7.1 (23), 8.09 (39), 10.2 (40) |
| [3H]E2G | OATP1B3 | 8.4 | 12.0 | 1.52 | 15.8 (37), 24.6 (17) |
Shown are the intracellular uptake kinetics of the cells derived from in vitro experiments: Km, Michelis-Menten constant; Vmax, maximum rate of uptake; CLint, intrinsic clearance per unit of time. Data represent the mean values from triplicate experiments.
[3H]estrone-3-sulfate ([3H]ES) for OATP1B1 and OATP2B1 and [3H]estradiol β-d-glucuronide ([3H]E2G) for OATP1B3 with the substrate in a concentration range of 0.1 to 100 μM were normalized to the control and used to determine cell function.
Reported Km values represent previously published reference data from the references cited in parentheses.