TABLE 4

Inhibition of MPP⁺ uptake via rOCT1 wild-type (WT) and rOCT1 mutants by three nontransported inhibitors

Uptake measurements were performed at 37°C in stably transfected HEK293 cells using an incubation time of 1 s, except in mutant D475E where a 5-s incubation was performed. Uptake of 0.1 [³H]MPP⁺ was measured in the presence of different concentrations of TBuA⁺, TPeA⁺, and corticosterone. Mean ± S.D. values of three to five separate experiments are shown. The compiled uptake measurements and the calculated Hill coefficients are shown in Figs. 5–7.

rOCT1	TBuA⁺ IC₅₀	TPeA⁺ IC₅₀	Corticosterone IC₅₀
	µM
WT	0.97 ± 0.22	0.27 ± 0.05	6.9 ± 1.57
F160A	0.42 ± 0.04^#	0.19 ± 0.04	2.36 ± 0.59^##
F160Y	9.8 ± 1.9^***	0.33 ± 0.09	8.65 ± 0.75
W218F	5.1 ± 0.20^***	0.03 ± 0.01^***	18.8 ± 4.3^**
W218Y	0.48 ± 0.06^#,^•••	0.20 ± 0.03^••	61.5 ± 11.6^***,^•••
W218L	5.13 ± 1.04^***	0.41 ± 0.05^##,^•••	4.07 ± 1.29^••
Y222F	0.28 ± 0.06^##	0.18 ± 0.02	7.07 ± 1.69
T226A	6.4 ± 1.6^***	0.30 ± 0.01	20.7 ± 6.0^**
R440K	1.28 ± 0.38	0.26 ± 0.05	6.00 ± 1.39
L447F	1.40 ± 0.29	0.51 ± 0.09^**	8.12 ± 2.32
L447Y	1.04 ± 0.14	0.49 ± 0.07^**	20.6 ± 4.0^**,^□
D475E	0.49 ± 0.10^#	0.12 ± 0.03*	2.26 ± 0.31^##

WT, wild-type.
ANOVA with post hoc Tukey test:
↵** P < 0.01,
↵*** P < 0.001 difference to wild-type;
↵^•• P < 0.01,
↵^••• P < 0.001 difference to W218F;
↵□ P < 0.05 difference to L447F; Student’s t test:
↵# P < 0.05,
↵## P < 0.01 difference to wild-type.