In order to answer the question of whether there is an optimal buffer system for the preservation and reoxygenation period in liver transplantation, sodium/potassium phosphate, HEPES, TRIS (THAM), MOPS and histidine/His-HC1 buffers were investigated. The buffers were added to an "extracellular" electrolyte composition of preservation solution. The solutions were incubated with in vitro cultures of pig hepatocytes in two different models. I: during cold hypoxia (4°C, PO2< 0.1 mmHg) for 24 h, and II. during the reoxygenation period of 3 h after preservation in UW solution. Cell viability, cell detachment rate, and LDH and GOT liberation were used as parameters of cell alteration. The lowest amount of enzyme release during the preservation period and reoxygenation was obtained using sodium or potassium phosphate buffer. Rising LDH and GOT liberation rates during preservation and reoxigenation were observed with HEPES and TRIS buffer. The enzyme release induced by these three buffer systems correlated with their pK a values. Higher pH of the preservation solution resulted in higher enzyme leakage from the cells. In contrast, the Histidine/HC1 buffer system with low pH led to striking cell damage during preservation as well as during reoxygenation. MOPS, a weak acid with the lowest pH in solution, led to the lowest enzyme release during the preservation period, but to high enzyme release after reoxygenation with standard medium. Incubation of the cultures with MOPS after UW preservation resulted in lower enzyme levels in comparison to the controls. In summary, PBS had the best results in our study.