Adenosine A1 receptors are necessary for protection of the murine heart by remote, delayed adaptation to ischaemia

Aims: Adenosine is involved in classic pre-conditioning (PC) in most species, acting through especially adenosine A 1 and A 3 receptors. We studied whether the adenosine A 1 receptor (A 1 R) was important for remote, delayed adaptation to ischaemia using a mouse with targeted deletion of the A 1 R gene. Methods: Remote, delayed adaptation was evoked by brain ischaemia (BIPC) through bilateral ligation of the internal carotid arteries. Through microdialysis probes placed in the brain and the abdominal aorta, we found that plasma adenosine increased following carotid artery ligation. Twenty-four hours after ligation, hearts were isolated, Langendorff perfused and subjected to 40 min global ischaemia and 60 min reperfusion. Hearts from sham operated and BIPC animals either with (A 1 R +/+ ) or without (A 1 R -/- ) the gene for the adenosine A 1 R were compared with each other. Results: In wild types, BIPC reduced infarct size and improved functional recovery during reperfusion, but BIPC did not protect hearts of A 1 R -/- mice. There were no significant differences between sham-operated A 1 R +/+ and A 1 R -/- in recovery of function or infarct size. The mitogen-activated protein kinases (MAPKs) extracellular signal-regulated protein kinasel/2 (ERK1/2), p38 and c-jun N-terminal kinase (JNK) were phosphorylated during reperfusion of sham treated hearts. The increase in ERK1/2 and p38 phosphorylation detected was attenuated in hearts of BIPC or A 1 R -/- animals. Conclusion: During BIPC adenosine acting on the A 1 R appears necessary for myocardial protection. MAPK signalling may possibly be involved in organ protection during the delayed phase of remote, delayed adaptation.