TABLE 2

Kinetic analysis of substrate-induced DAT-mediated [³H]MPP⁺ efflux

The data of three experiments (n = 3) were pooled (n = 117 data points) and fit simultaneously to either the one- or two-component model. In all cases, the two-component model fit the data better than the one-component model (P < 0.001). For the full substrates (d-amphetamine, PAL-1046, and PAL-738) a Student's t test (unpaired), using the parameter value and its S.D. (GraphPad online t test calculator; GraphPad Software Inc., San Diego, CA), was used to test statistical significance between parameter values.

	A1	K1	A2	K2
	% ± S.D.	min⁻¹	% ± S.D.	min⁻¹
d-Amphetamine
5 nM	56 ± 3	0.064 ± 0.008	45 ± 4	0.0016 ± 0.0010
20 nM	79 ± 3^*	0.10 ± 0.01^*	21 ± 3^*	0.0023 ± 0.0015
100 nM	84 ± 2^*	0.24 ± 0.02^*^#	15 ± 2^*	0.0078 ± 0.0020^*
PAL-1046
10 nM	23 ± 9	0.13 ± 0.08	78 ± 9	0.0030 ± 0.0016
50 nM	63 ± 8^*	0.16 ± 0.05	35 ± 7^*	0.0050 ± 0.003
250 nM	79 ± 8^*	0.29 ± 0.07	20 ± 6^*	0.012 ± 0.006
PAL-1045¹
50 nM	26 ± 65	0.025 ± 0.062	79 ± 67	0.0016 ± 0.0060
250 nM	51 ± 17	0.051 ± 0.025	52 ± 18	0.0024 ± 0.0036
1250 nM	84 ± 13	0.058 ± 0.015	19 ± 14	0.00094 ± 0.0070
PAL-738
50 nM	18 ± 4	0.073 ± 0.029	81 ± 4	0.0018 ± 0.0005
250 nM	49 ± 6^*	0.060 ± 0.10	48 ± 6^*	0.0035 ± 0.0013
1250 nM	73 ± 6^*^#	0.069 ± 0.008	25 ± 6^*^#	0.0060 ± 0.0003
PAL-192¹
600 nM	39 ± 29	0.024 ± 0.017	64 ± 29	0.000 ± 0.003
3000 nM	70 ± 21	0.027 ± 0.009	32 ± 22	0.000 ± 0.005
15,000 nM	91 ± 15	0.032 ± 0.006	13 ± 15	0.000 ± 0.100
PAL-193¹
600 nM	26 ± 36	0.027 ± 0.036	76 ± 36	0.001 ± 0.003
3000 nM	67 ± 25	0.030 ± 0.013	38 ± 26	0.001 ± 0.005
15,000 nM	86 ± 17	0.036 ± 0.009	16 ± 18	0.0003 ± 0.009

↵* P < 0.01 compared with the corresponding parameter of the lowest concentration of test drug.
↵# P < 0.01 compared with the corresponding parameter of the middle concentration of test drug.
↵1 For the partial substrates (PAL-192, PAL-193, and PAL-1045), the t tests among individual parameters were all nonsignificant, so the F-test, as described under Materials and Methods, was used to test for statistical significance between corresponding curves. For all of these drugs, each curve was statistically different from the other curves (P < 0.0001).