Table 3.

K_i Values for the Inhibition by Nucleoside Derivatives of Binding of Antagonist [³H]DPCPX at Wild-Type and Mutant Human A₁ ARs Transiently Expressed in HEK-293 Cells^a

	binding affinity, Ki (nM ± sem), or % inhibition
compound	wild-type hA1	H278E	H278D	H278A	H278L	T277E	T277A
DPCPXb	4.5 ± 1.2	36 ± 2	50 ± 3	40 ± 8	35 ± 2	18.3 ± 1.6	3.5 ± 0.9
CGS15943b	3.4 ± 1.1	120 ± 20	110 ± 40	160 ± 3	90 ± 3	8.6 ± 0.3	4.6 ± 1.5
1	4600 ± 480	22%	15%	13%	<10%	13%	<10%
2	<10%	17%	<10%	11%	12%	<10%	<10%
3	<10%	14%	20%	20%	17%	<10%	<10%
5	<10%	24%	16%	15%	25%	<10%	<10%
6	30%	14%	<10%	14%	17%	<10%	<10%
7	17%	18%	<10%	<10%	15%	<10%	<10%
9, CCPA	610 ± 50	1200 ± 150	1000 ± 170	1400 ± 120	820 ± 90	7000 ± 800	11%
10	12%	380 ± 80	340 ± 20	570 ± 60	400 ± 60	41%	<10%
13	15000 ± 3100	560 ± 170	450 ± 40	570 ± 30	550 ± 50	48%	<10%
14	6200 ± 1900	210 ± 60	240 ± 30	220 ± 30	290 ± 50	50%	17%
16	13%	750 ± 150	590 ± 20	1000 ± 60	700 ± 100	39%	<10%
18	13%	44%	48%	50%	39%	22%	<10%
19	38%	530 ± 30	410 ± 120	834	NDc	<10%	<10%
20	<10%	980 ± 280	810 ± 250	940	NDc	<10%	NDc
21	<10%	560 ± 80	500 ± 120	670	NDc	11%	NDc
22, NECA	1600 ± 100	9700 ± 900	8500 ± 1400	8800 ± 700	8800 ± 900	25%	<10%
23	<10%	26%	13%	14%	32%	12%	<10%
26	14%	1200 ± 400	1200 ± 300	980 ± 450	58%	10%	<10%
27	<10%	220 ± 20	350	NDc	NDc	16%	NDc

^aStructures are given in Figure 2. Experiments were performed using HEK-293 cells transiently expressing (using Lipofectamine 2000) a mutant hA₁ AR. Binding was carried out using 0.3–0.5 nM [³H]DPCPX as the radioligand. K_i values are expressed as the mean ± sem (n = 3–6) and normalized against a nonspecific binder, CGS15943. Values in italics are percent inhibition at 10 μM, relative to the maximum inhibition by CGS15943 at 10 μM (100%).

^bNon-nucleoside AR antagonists.

^cNot determined.