Bench-to-bedside review: Adenosine receptors – promising targets in acute lung injury?

Table 1 Relevant functional parameters of adenosine receptors

	A₁	A_2A	A_2B	A₃
Coupled G proteins	G_i, G_o	G_s, G_olf, G_15/16	G_s, G_q	G_i, G_q
Intracellular messengers	↓ cAMP	↑ cAMP	↑ cAMP	↓ cAMP
	↑ IP₃/DAG	↑ IP₃	↑ IP₃/DAG	↑ IP₃/DAG
	↑ Arachidonate
	↑ PEtOH
Selected biologic functions	Bradycardia Antinociception Ischemic preconditioning ↓ Lipolysis, ↓ Glomerular filtration	↓ Platelet aggregation Vasodilation Protection against ischemic damage	Relaxation of vascular smooth muscle cells Stimulation of mast cell mediator release	↑ Mediator release from mast cells (mice) Preconditioning
Potency^a (EC₅₀ [μmol/l])	0.31	0.73	23.5	0.29

^aPotency as reflected by intracellular cAMP levels. Adapted from [8, 9, 18, 55]. DAG, diacylglycerol; ED₅₀, 50% effective dose; IP₃, inositoltriphosphate; PetOH, phosphatidylethanol.

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