Isoflurane-induced protection against myocardial stunning is independent of adenosine 1 (A1) receptor in isolated rat heart

Abstract

Volatile anaesthetics can pharmacologically enhance the recovery of stunned myocardium, but the mechanism is still unknown. This study sought to determine whether isoflurane attenuates myocardial stunning, and whether the myocardial protection of isoflurane is mediated by adenosine A1 receptors. Five groups (n=8) of isolated rat hearts were studied in the Langendorff apparatus. The control groups underwent 20-min ischaemia with or without adenosine receptor antagonist (DPCPX, A1selective) treatment (Cont group and DPCPX group). In the isoflurane groups, isoflurane (1.5 MAC) was present throughout the experiment (Iso group) and DPCPX (200 nM) was administered from 10 min before ischaemia (Iso+DPCPX(pre-1) group) or the beginning of reperfusion (Iso+DPCPX(post-1) group) to the end of experiment. The isoflurane groups had a lower end-diastolic pressure than the control groups (P<0.05). Developed pressure recovered to 77, 76, and 82% in lso, lso+DPCPX(pre-1) and lso+DPCPX(post-1) groups, respectively (P<0.05 compared with control groups). LV+dp/dtmax recovered to 53, 86, 81, 84, and 60% of pre-ischaemic values in Cont, Iso, lso+DPCPX(pre-1), lso+DPCPX(post-1), and DPCPX groups. LV-dp/dtmin recovered to 55, 84, 83, 81, and 62%, respectively. Both LV+dp/dtmax and LV-dp/dtmin were significantly different (P<0.05) between control and isoflurane groups during reperfusion. There were no significant differences among the isoflurane groups. Our data show that isoflurane enhances the post-ischaemic functional recovery of isolated rat heart and that block of A1 receptors does not abolish the beneficial effects of isoflurane. We conclude that A1 receptors are not involved in isoflurane-induced myocardial protection in the isolated rat heart.