REPERFUSION INJURY TO ENDOTHELIAL-CELLS AFTER COLD-STORAGE OF RAT LIVERS - PROTECTION BY MILDLY ACIDIC PH AND LACK OF PROTECTION BY ANTIOXIDANTS

Lethal reperfusion injury to sinusoidal endothelial cells occurs after cold ischemic storage of livers and may be responsible for liver graf t failure from storage injury. Here, we evaluated potential mechanisms underlying this reperfusion injury. In rat livers stored in Euro-Coll ins solution for 24 h and reperfused with Krebs-Henseleit bicarbonate buffer, nonparenchymal cell killing showed periportal predominance as assessed by nuclear staining with trypan blue. In livers reperfused in the retrograde direction, the lobular distribution of cell killing wa s reversed, indicating that cell killing was more rapid in oxygen-rich upstream regions. However, antioxidants, including allopurinol, desfe rrioxamine, catalase, superoxide dismutase, superoxide dismutase plus catalase, and U74006F, did not reduce cell killing. Similarly reperfus ion with anoxic buffer did not prevent lethal injury. Antioxidants and anoxic reperfusion also did not improve cell viability in livers stor ed in UW solution. Nevertheless, superoxide generation, as identified by formazan formation from nitroblue tetrazolium, was increased in Kup ffer cells after lives storage and reperfusion as compared to unstored livers. Acidification of the reperfusion buffer from pH 7.4 to pH 7.1 5 reduced overall nonparenchymal cell killing from about 40 % to 10 %. Moreover, a pH gradient developed across the liver lobule during repe rfusion with the effluent 0.2-0.4 pH units more acidic than the influe nt. This intralobular pH gradient appears to account for the relative sparing of cells in more acidic downstream regions of the lobule. Lowe r temperatures of reperfusion also reduced lethal injury. In conclusio n, Kupffer cells generated superoxide after perfusion of stored rat li vers, but formation of oxygen free radicals did not appear to contribu te to lethal reperfusion injury to endothelial cells. Rather, mildly a cidotic pH was protective against lethal injury. Thus, hydrogen ion co ncentration may be a critical determinant of reperfusion injury to sin usoidal endothelial cells.