Comparison of Km values for TEA uptake, Km values for MPP uptake, IC50 values for inhibition of MPP uptake by TEA, and IC50 values for inhibition of TEA uptake by MPP between rOCT1 wild type and mutants of rOCT1
The transporters were expressed in X. laevis oocytes and uptake was measured at various concentrations of TEA or MPP. In addition, uptake of 0.1 μM [3H]MPP was measured in the presence of various concentrations of TEA, uptake of 10 μM [14C]TEA was measured in the presence of various concentrations of MPP. Km and IC50 values were determined by fitting the Michaelis-Menten equation or the Hill equation to the data, respectively. Hill coefficient varied between 0.75 and 1.25 but was not significantly different between different groups. Mean ± S.E.M. from three to seven independent experiments are indicated.
| Km or IC50 | rOCT1 | ||
|---|---|---|---|
| Wild Type | L447Y/Q448E | A443I/L447Y/Q448E | |
| μM | |||
| Km for TEA uptake | 75 ± 11 (7) | 72 ± 6 (3) | 28 ± 3 (3)*† |
| IC50 for inhibition of MPP uptake by TEA | 115 ± 18 (4) | 97 ± 21 (4) | 26 ± 8 (4)**† |
| Km of MPP uptake | 5.6 ± 1.0 (6) | 1.1 ± 0.1 (3)* | 1.1 ± 0.2 (3)* |
| IC50 for inhibition of TEA uptake by MPP | 9.2 ± 1.7 (4) | 0.9 ± 0.1 (3)** | 0.6 ± 0.2 (3)* |