CALPAIN IS A MEDIATOR OF PRESERVATION-REPERFUSION INJURY IN RAT-LIVERTRANSPLANTATION

Pretenses as well as alterations in intracellular calcium have importa nt roles in hepatic preservation-reperfusion injury, and increased cal pain activity recently has been demonstrated in liver allografts, Expe riments were designed to evaluate (i) hepatic cytosolic calpain activi ty during different periods of cold ischemia (CI), rewarming, or reper fusion, and (ii) effects of inhibition of calpain on liver graft funct ion using the isolated perfused rat liver and arterialized orthotopic liver transplantation models, Calpain activity was assayed using the f luorogenic substrate Suc-Len-Leu-Val-Tyr-7-amino-4-methyl coumarin (AM C) and expressed as mean +/- SD pmol AMC released/min per mg of cytoso lic protein, Calpain activity rose significantly after 24 hr of CI in University of Wisconsin solution and further increased with longer pre servation, Activity also increased within 30 min of rewarming, peaking at 120 min, Increased durations of CI preceding rewarming resulted in significantly higher activity (P < 0.01). Calpain activity increased rapidly upon reperfusion and was significantly enhanced by previous CI (P < 0.01). Calpain inhibition with Cbz-Val-Phe methyl ester signific antly decreased aspartate aminotransferase released in the isolated pe rfused rat liver perfusate (P < 0.05). Duration of survival after orth otopic liver transplantation using livers cold-preserved for 40 hr was also significantly increased (P < 0.05) with calpain inhibitor, In co nclusion, calpain proteases are activated during each phase of transpl antation and are likely to play an important role in the mechanisms of preservation-repel fusion injury.