Oxygen modulation of superoxide radical injury in the krebs-perfused, isolated rabbit heart.

Myocardial malondialdehyde concentration (MDA) as an index of membrane lipoperoxidation was measured in previously ischemic isolated rabbit hearts reperfused with Krebs solution equilibrated with different oxygen concentrations. Hearts were subjected to a ischemic period of 30 min at 4 degrees C and then reperfused at 37 degrees C with a Krebs-Henseleit solution equilibrated with 95% oxygen (group 1), 65% oxygen (group 2), or 21% oxygen (group 3). MDA concentration in nanomoles per gram protein (mean +/- SEM) at the end of reperfusion in group 1 (n = 5) was 357 +/- 18; in group 2 (n = 5) 282 +/- 18; and in group 3 (n = 5) 246 +/- 16 (p =.0008, group 1 vs. group 3; p =.0109, group 1 vs. group 2). The results support that oxidative stress after ischemia and reperfusion is modulated by the oxygen concentration of the reperfusate in the crystalloid-perfused isolated rabbit heart such that higher oxygen concentrations are associated with greater oxidative stress.