COLD-STORAGE SENSITIZES HEPATOCYTES TO OXIDATIVE STRESS INJURY

Liver cold storage leads to oxygen free radical production and reperfu sion injury. Antioxidants are effective in suppressing reperfusion inj ury in rat livers when used in the reperfusion medium. However, in cli nical liver transplantation their effectiveness is not clear, which ma y be due to the way they are used (in the recipient). In this study we compare the effectiveness of antioxidants when used in the reperfusio n medium versus the cold storage solution in isolated hepatocytes and the isolated perfused liver. Hepatocytes were cold stored in UW soluti on for 24 h. Oxidative stress, induced by t-butyl hydroperoxide (tBHP) , was measured in the presence of one of five different antioxidants - deferoxamine (DFO), dithiothreitol(DTT), trolox, tocopherol, dimethyl thiourea (DMTU) - in the reperfusion buffer or UW solution. Efficacy w as judged by reduction in membrane damage (LDH release) during rewarmi ng. Also, rat livers were cold stored for 48 h in UW solution (+/- ant ioxidant) and reperfused (+/- antioxidants). Efficacy was judged by th e effect on enzyme release and bile production. Cold storage of hepato cytes for 24 h sensitized them to oxidative stress. The concentration of tBHP required to induce maximal cell death (80 %-90 % LDH release) was reduced from 1.3 mM (fresh cells) to 0.37 mM (LD-50 values). All a ntioxidants except DMTU suppressed oxyradical-induced LDH release when used in the reperfusion medium, but only DFO was effective when used in the UW solution. In the isolated perfused liver, DFO, DTT, and trol ox were effective and suppressed enzyme release when added to the repe rfusion buffer, but none were effective when used in the UW solution. We conclude that cold storage sensitizes liver cells to oxidative stre ss. The most effective antioxidant was the iron chealator, DFO, which was effective in the reperfusion buffer (isolated perfused liver or he patocytes) but not in the UW solution when tested in the isolated perf used liver. Suppression of reperfusion injury in liver transplantation could be obtained by antioxidant therapy. However, it is unclear how best to deliver the antioxidants to the site of oxyradical generation.