Parenchymal and vascular endothelial cell injury in the hypoxic and reperfused rat liver. Evidence for superoxide anion generation by perfusion with ferricytochrome c.

Isolated perfused livers from rats fasted overnight were subjected to 90 min of low-flow hypoxia followed by reoxygenation for 30 min. Intra-hepatic generation of superoxide anion was analysed by continuous perfusion with 40 mumol/l of oxidized cytochrome c, the reduction of which was measured spectrophotometrically in the effluate. Reduction of cytochrome c as an indicator for hepatic superoxide anion generation remained constant during pre-hypoxic perfusion and during hypoxia. Upon reperfusion, an initial peak was observed to 47.2 +/- 3.8 nmol/g/min followed by a stable plateau above pre-hypoxic values. Both peak and plateau were significantly attenuated in the presence of 80,000 U/l superoxide dismutase (SOD). Accordingly, tissue contents of lipid peroxides were significantly lower at the end of reperfusion (976 +/- 73 vs 1153 +/- 71 nmol/g*), enzyme leakage [U/g/min] from the endothelium (PNP: 8.4 +/- 4.2 vs 17.2 +/- 3.4**) and from the hepatic parenchyma (Alt: 108 +/- 35 vs 170 +/- 23*) was significantly reduced during reperfusion and oxygen consumption was elevated in the presence of SOD (3.27 +/- 0.34 vs 2.71 +/- 0.37*). It is concluded that reactive oxygen species arise in the vascular lumen or the space of Disse after prolonged hypoxia of the liver, altering the functional outcome of the organ upon reoxygenation. SOD is able to protect against these alterations. * P < 0.05; ** P < 0.01.