Value of energy substrates in HTK and UW to protect human liver endothelial cells against ischemia and reperfusion injury

Adenosine 5'-triphosphate (ATP) depletion is a major cause of cellular injury during ischemia and reperfusion in organ transplantation. Therefore, histidine-tryptophan-ketoglutarate solution (HTK; alpha-ketoglutarate) and University of Wisconsin solution (UW; adenosine) were supplied with energy substrates to achieve graft viability. Nevertheless, their efficacy for maintaining the ATP level, particularly in human liver endothelial cells, was uncertain. Furthermore, it is of interest whether a high ATP level is beneficial in human liver endothelial cell viability. We used human liver endothelial cells between the 3rd and 6th passages in a cell culture model. Human liver endothelial cells were exposed to hypothermic preservation (4 degrees C) in HTK and UW for 2, 6, 12, 24 and 48 h with subsequent reperfusion of 6 h. ATP and lactate dehydrogenase (LDH) were measured after each interval. In comparison to HTK, UW demonstrates a statistically significantly higher level of ATP after each interval of ischemia (p < 0.001) and reperfusion (p < 0.002). Additionally, UW-preserved human liver endothelial cells exceed the ATP level of the warm control during all intervals of ischemia. The loss of cell viability (LDH) was statistically significantly higher after ischemia (p < 0.01) and reperfusion (p < 0.01) in HTK than in UW except after the interval of 48 h. In conclusion, adenosine was more effective than alpha-ketoglutarate in maintaining a high ATP level in human liver endothelial cells after ischemia and reperfusion. Different pathways of energy substrate utilization were a contributing factor. The beneficial effect of the higher ATP level caused by adenosine to human liver endothelial cell viability was limited to 24 h of ischemia. Beyond this ischemia time we could not prove a favorable impact of adenosine on human liver endothelial cells.