Table 1.

Stimulation of human P-gp-His10 ATPase activity by the rosamine and rhodamine analogues of Charts 1 and 3.

	Human P-gp-His10
Compd	Vmax, a Fold	KM, b μM	IC50,c μM
Ver	17.9 ± 2.0	24 ± 2.6
1-S	7.7 ± 1.0	8.5 ± 1.2
1-Se	7.2 ± 1.1	9.1 ± 1.1
1-Te	8.4 ± 1.9	8.3 ± 0.8
2-S	2.2 ± 0.3	1.3 ± 0.5
2-Se	< 1.5	N.D.d	2.3 ± 0.4
2-Te	3.0 ± 0.7	4.4 ± 0.8
3-S	7.5 ± 1.5	9.3 ± 1.0
4-S	6.4 ± 0.6	32 ± 3
5-S	9.0 ± 0.5	8.3 ± 1.2
5-Se	6.8 ± 1.0	10.1 ± 0.7
5-Te	4.5 ± 0.3	9.0 ± 0.8
6-Se	< 1.5	N.D.d	6.8 ± 0.2
7-S	7.7 ± 0.5	3.4 ± 0.6
7-Se	7.6 ± 0.6	3.5 ± 0.2
7-Te	5.5 ± 0.3	2.0 ± 0.1
8-Se	< 1.5	N.D.d	23.6 ± 3.3
10-S	5.9 ± 1.3	3.9 ± 0.1
10-Se	2.5 ± 0.2	3.3 ± 0.6
10-Te	5.7 ± 0.7	3.2 ± 1.0
11-S	8.2 ± 0.4	4.9 ± 0.8
11-Se	7.5 ± 0.9	8.3 ± 0.5
12-S	4.8 ± 0.3	10.0 ± 1.3
12-Se	3.3 ± 0.6	10.4 ± 1.0
13-S	6.2 ± 0.8	3.2 ± 0.4
22-S	4.3 ± 0.3	111 ± 4
22-Se	2.1 ± 0.3	56 ± 11
23-S	2.7 ± 0.2	140 ± 11
23-Se	2.8 ± 0.6	89 ± 7
23-Te	1.8 ± 0.1	9.6 ± 1.1
26-Se	10.5 ± 1.6	0.68 ± 0.14
30-S	9.0 ± 0.5	0.36 ± 0.08	7.9 ± 1.1
30-Se	5.0 ± 0.6	0.35 ± 0.02	9.0 ± 0.2
30-Te	7.0 ± 0.4	0.41 ± 0.03	5.3 ± 1.2
31-S	3.1 ± 0.3	0.087 ± 0.012	0.67 ± 0.14

^aV_max is the ratio of the maximum stimulation in the presence of compound relative to that in the absence of compound (the basal activity).

^bK_M is the apparent Michaelis-Menten constant or the concentration of compound required for half maximal stimulation of ATPase activity.

^cIC₅₀ is the concentration of compound required for 50% inhibition of verapamil-stimulated (400 μM in human P-gp-His10) ATPase activity.

^dN.D., not determined because of low stimulation of ATPase activity.