Effect of mutations that change the interaction of corticosterone with rOCT1 on the affinity of MPP+
Inhibition of [14C]TEA+ uptake by MPP+ was measured in oocytes expressing wild-type rOCT1 or rOCT1 mutants. Oocytes were incubated 15 min with 5 μM [14C]TEA+ in the presence of eight different concentrations of MPP+. IC50(MPP) values of individual experiments were determined by fitting the Michaelis-Menten equation to the data. Mean values ± S.E.M. are presented. Numbers of independent experiments are indicated in parenthesis.
Mutation | IC50(MPP) |
|---|---|
| Wild type | 7.4 ± 1.1 (3) |
| C451M | 9.4 ± 1.3 (4) |
| C451M, L447Y | 0.46 ± 0.09** |
| C451M, Q448E | 2.5 ± 0.52* (3) |
| C451M, L447Y, Q448E | 0.31 ± 0.05** (3) |
| C451M, F160A | 19.5 ± 2.0** (3) |
| C451M, W218Y | 23.1 ± 2.2*** (3) |
| C451M, R440K | 18.6 ± 2.2** (3) |
↵* P < 0.05, significance for difference compared to rOCT1(C451M) mutant calculated by ANOVA with post hoc Tukey test.
↵** P < 0.01, significance for difference compared to rOCT1(C451M) mutant calculated by ANOVA with post hoc Tukey test.
↵*** P < 0.001, significance for difference compared to rOCT1(C451M) mutant calculated by ANOVA with post hoc Tukey test.