TABLE 1

K_i values, EC₅₀ values, and efficacies of agonists at human A_2B adenosine receptors

		K_i or EC₅₀ Value ± S.E.M. (Maximal Effect ± S.E.M.)^{^a}
		BAY60-6583	NECA	Adenosine
		nM
Transfected CHO cells (CHO-hA_2B)	Radioligand binding versus [³H]PSB-603	212 ± 20	1890 ± 240	n.d.^{^b}
	cAMP	98.7 ± 0.6 (56 ± 16%)	318 ± 55 (100%)	n.d.^{^b}
	[Ca²⁺]_i^{^c}	No signal (at 0.1–100 μM)	No signal (at 0.1–100 μM)	No signal (at 0.1–100 μM)
Native HEK293 cells	cAMP	n.d.^{^b} (6 ± 4% at 100 μM)	n.d.^{^b} (100% at 0.1–100 μM)	n.d.^{^b} (64 ± 3% at 300 μM)
	[Ca²⁺]_i	n.d.^{^b} (1 ± 5% at 100 μM)	n.d.^{^b} (100% at 100 μM)	n.d.^{^b} (100 ± 14% at 300 μM)
Transfected HEK293 cells (HEK-hA_2B)	cAMP	505 ± 231 (49 ± 14%)	200 ± 52 (100%)	2510 ± 593 (100 ± 12%)
	[Ca²⁺]_i	579 ± 262 (57 ± 7%)	438 ± 177 (100%)	990 ± 231 (98 ± 4%)
Jurkat T cells	cAMP	7500 ± 1400 (IC₅₀ versus NECA)	3810 ± 560 (n.d.)	237,000 ± 26000 (n.d.)
	[Ca²⁺]_i	n.d.^{^b} (1 ± 8% at 100 μM)	663 ± 284 (100%)	n.d.^{^b} (102 ± 10% at 300 μM)

↵^a Compared with the maximal effect of NECA set at 100%.
↵^b n.d., Not determined.
↵^c ATP and UTP (100 μM each) were used as a positive control. They gave a robust calcium signal (via activation of endogenous G_q-coupled P2Y₂ receptors).