Rat liver was kept at 4 degrees C or 37 degrees C in MEM, and reperfused through a closed circulation from the hepatic vein to the portal vein at 37 degrees C with the same solution. Although purine nucleoside phosphorylase and ALT activities were increased in the perfusate, depending on the duration of ischemia at both 4 degrees C and 37 degrees C, the ratio of the latter to the former was significantly higher after 37 degrees C-ischemia than after 4 degrees C-ischemia. The stimulation stage of Kupffer cells evaluated in situ by formazan deposition after liver perfusion with nitro blue tetrazolium and phorbol myristate acetate was elevated after 4 degrees C-ischemia longer than 1 h, but not after 37 degrees C-ischemia. In contrast, the degree of oxidative stress in hepatocytes assessed by formazan deposition after liver perfusion with nitro blue tetrazolium alone was greater after 37 degrees C-ischemia than after 4 degrees C-ischemia. These results suggest that oxidative stress in hepatocytes and the stimulatory state of Kupffer cells after ischemia-reperfusion may differ between 4 degrees C-ischemia and 37 degrees C-ischemia, probably leading to different development of liver damage.