The involvement of the intracellular superoxide production system in hepatic ischemia-reperfusion injury. In vivo and in vitro experiments using transgenic mice manifesting excessive CuZn-SOD activity.

In vivo and in vitro studies were conducted using transgenic mice with 1.8-fold increased SOD activity in the cytoplasmic fraction compared to normal mice in order to evaluate the role of cytoplasmic superoxide dismutase (SOD) in hepatic ischemia-reperfusion injury. In the in vivo study, after inducing 15 min 70% partial hepatic ischemia followed by 45 min reperfusion, we determined the plasma levels of ALT, hyaluronic acid, and phosphatidylcholine hydroperoxide (PCOOH) as the membranous lipoperoxide of the hepatic tissue. In addition, in vitro ischemia-reperfusion studies for cultured hepatocytes were conducted in an anaerobic chamber that could create a hypoxic or oxygen-rich environment in order to clarify the amelioration of reperfusion injuries in the SOD rich hepatocytes. High levels of ALT and PCOOH were found as a result of reperfusion in normal mice, while a suppression of the increase in these levels was noted in the transgenic mice. In both groups, the hyaluronic acid levels were not modified. These results suggest that intracellular superoxide production is involved in the mechanism of hepatic ischemia-reperfusion injury, and that an improvement of the ability to eliminate intracellular superoxide species can contribute to the prevention of reperfusion injury.