The isovolumetric hemodilution treatment reduces ischemic injury and anti‐radical interventions may reduce reperfusion injury. However, the effects of the treatment with both interventions have never been investigated. In the present study, anesthetized rabbits underwent 45 min of coronary artery ligation, which was followed by 180 min of reperfusion. Ten animals in each group received: (i) normal saline only; (ii) isovolumetric hemodilution with Dextran 40 during ischemia; (iii) superoxide dismutase (SOD) 1 min before and during reperfusion; and (iv) combined treatment with hemodilution and SOD. Results: (1) compared with those of the control group, left ventricular peak pressure (LVP) and
$\pm {\rm d}p/{\rm d}t$
‐max improved significantly in the animals which received hemodilution or SOD alone, and left ventricular systolic function of the animals with the combination therapy improved further; (2) infarct size averaged
$54.4\pm 2.6$
% of the risk region in controls and was significantly smaller in the rabbits that were treated with hemodilution (
$32.8\pm 1.8$
%) (
$p<0.05$
), with SOD (
$42.1\pm 3.2$
%) (
$p<0.05$
) and with the combination therapy (
$23.4\pm 1.5$
%) (
$p<0.01$
). Therefore, (1) in groups where either hemodilution during ischemia or removal of oxygen radicals during reperfusion was done left ventricular systolic function and salvaged ischemic reperfused myocardium improved significantly; (2) in this acute model, SOD improved left ventricular systolic and diastolic functions and reduced infarct size further when given to the animals that had been treated with hemodilution.
