TABLE 7.

Binding affinity of agonists and antagonists at human adenosine receptor subtypes (K_i values with 95% confidence intervals or ± S.E.M. in parentheses)

	A₁	A_2A	A_2B	A₃	Reference
Agonists with unmodified ribose
R-PIA	2.0 (1–4.2)	860 (480–1,540)		16 (9.3–29)	—^a
			33,700 (±6,800)		—^c
			3,800 (±1,700)		—^e
S-PIA	75 (42–134)	7,800 (7,000–8,640)		45 (33–61)	—^a
			62,800 (±21,600)		—^c
CPA	2.3 (1.5–3.4)	790 (470–1,360)		43 (30–61)	—^a
			34,400 (±11,100)		—^c
			21,000 (±4,300)		—^e
CCPA	0.8 (0.55–1.25)	2,300 (2,000–2,700)		42 (32–56)	—^a
			40,100 (±16,400)		—^c
2-Cl-adenosine	1.39 (1.28–1.51)	180 (150–220)		19 (14–28)	—ⁱ
Agonists with 5’-modified ribose
NECA	14 (6.4–29)	20^* (12–35)		6.2^* (3.5–11)	—^a
			330 (±60)		—^c
			360 (±120)		—^e
CGS 21680	290 (230–360)	27 (12–59)		67 (50–90)	—^a
			361,000 (±21,000)		—^c
HENECA	60 (50–72)	6.4 (3.8–11)		2.4 (2.0–2.9)	—^b
PENECA	560 (480–650)	620 (300–1,300)		6.2 (5.1–7.5)	—^b
PHPNECA	2.7 (1.7–7.1)	3.1 (2.4–3.9)		0.42 (0.17–1.0)	—^b
AB-MECA	1,500 (1,300–1,800)	3,600 (2,700–4,700)		22 (20–24)	—^a
IB-MECA	3.7 (1.8–7.7)	2,500 (1,900–3,400)		1.2 (0.96–1.5)	—^a
			54,000 (±5,600)		—^c
IAB-MECA	8.5 (4.8–15)	470 (300–740)		0.64 (0.58–0.70)	—^a
Cl-IB-MECA	115 (114–116)	2,100 (1,700–2,500)		11 (9.4–13)	—^b
Antagonists: xanthines
DPCPX	3.9^* (3.5–4.2)	129 (35–260)		4,000 (2,600–6,000)	—^a
			50 (±3.7)		—^c
			51 (±6.1)		—^e
XAC	29 (24–35)	1 (0.58–1.7)		92 (64–130)	—^a
			7.3 (±2.8)		—^c
			12 (±4.6)		—^e
MRS1754	400 (±190)	500 (±11)	2.0 (±0.31)	570 (±180)	—^f
MSX-2	2,500 (1,700–3,600)	5.0 (±0.6)		>10,000	—^h
Theophylline	6,800 (4,100–11,000)	1,700 (1,000–2,900)		86,000 (74,000–101,000)	—^a
Antagonists: non-xanthines
CGS 15943	3.5 (1.7–7.3)	4.2 (2.6–6.6)		51 (43–60)	—^a
			16 (±3.6)		—^e
SCH 58261	290 (210–410)	0.6 (0.5–0.7)		>10,000	—^d
ZM 241385	260 (190–390)	0.8 (0.7–1.0)		>10,000	—^d
			32 (±6)		—^c
MRE 3008F20	1,100 (±1,100)	140 (±15)	2,100 (±300)	0.29 (±0.03)	—^g

Values are from saturation experiments.

Klotz et al., 1998, transfected CHO cells; radioligands [³H]CCPA (A₁), [³H]NECA (A_2A and A₃).

Klotz et al., 1999, transfected CHO cells; radioligands [³H]CCPA (A₁), [³H]NECA (A_2A and A₃).

Linden et al., 1999, transfected HEK 293 cells; radioligand ¹²⁵I-ABOPX.

Ongini et al., 1999, transfected CHO cells (A₁ and A_2A) or HEK 293 cells (A_2A and A₃); radioligands [³H]DPCPX (A₁), [³H]SCH 58261 (A_2A), ¹²⁵I-AB-MECA (A₃).

Ji and Jacobson, 1999, transfected HEK 293 cells; radioligand [³H]ZM 241685.

Kim et al., 2000, transfected HEK 293 cells; radioligands ¹²⁵I-ABA (A₁), ¹²⁵I-ZM 241685 (A_2A), ¹²⁵I-ABOPX (A_2B), ¹²⁵I-AB-MECA (A₃).

Varani et al., 2000, transfected CHO cells; radioligands [³H]DPCPX (A₁ and A_2B), [³H]SCH 58261 (A_2A), ¹²⁵I-AB-MECA (A₃).

Sauer et al., 2000, transfected CHO cells; radioligand [³H]CHA (A₁), [³H]CGS 21680 (A_2A), [³H]NECA (A₃).

ⁱ

K.-N. Klotz and S. Kachler, unpublished, transfected CHO cells; radioligand [³H]NECA.