Angiotensin II reduces infarct size and has no effect on post-ischaemic contractile dysfunction in isolated rat hearts

1 In order to test the hypothesis that angiotensin II exacerbates myocardial ischaemia-reperfusion (IR) injury, we examined the effects of graded angiotension II concentrations of angiotensin II on IR injury in both working and non-working (Langendorff) isolated rat hearts. 2 Non-working hearts were subjected to 30 min aerobic perfusion (baseline) then 25 min of global, no-flow ischaemia followed by 30 min of reperfusion either in the absence (control, n=7) or presence of 1 (n=6) or 10 nM (n=5) angiotensin II). Recoveries of LV developed pressure and coronary flow after 30 min reperfusion in control hearts (58 +/-9 and 40 +/-8% of baseline levels, respectively) were no different from hearts treated with 1 or 10 nM angiotensin II. Infarct size (determined at the end of reperfusion by triplienyltetrazolium chloride staining) was reduced by angiotensin II in a concentration-dependent manner (from a control value of 27 +/-3 to 18 +/-4% and 9 +/-3% of the LV, respectively). 3 Working hearts were subjected to 50 min pre-ischaemic (pre-I) aerobic perfusion then 30 min of global, no-flow ischaemia followed by 30 min of reperfusion either in the absence (control, n=14) or presence of 1 (n=8). 10 (n=7) or 100 nm (n=7) angiotensin II). In controls, post-ischaemic (post-I) left ventricular (LV) work and efficiency of oxygen consumption were depressed (43 +/-9 and 42 +/- 10% of pre-I levels, respectively). The presence of angiotensin II throughout IR had no effect on LV work compared with control. 4 Thus, angiotensin II reduces infarct size in a concentration-dependent manner but has no effect on contractile stunning associated with IR in isolated rat hearts.