Oxidation-reduction changes in pyridine nucleotide fluorescence were investigated in perfused and preserved porcine liver. A fluorocarbon emulsion (FC-43) was administered to the perfusate as an oxygen carrier to obtain full oxidation level by portal perfusion at a physiological low flow rate. A satisfactory reading was obtained by portal perfusion with EuroCollins' solution containing 10% v/v FC-43 at a rate of 0.5 ml/min/g liver. The amplitude (R×A) and the changing velocity (R×V) from full oxidation to full reduction were determined in the resultant trace curve. Both R×A and R×V decreased in inverse proportion to the duration of preservation period (3, 6, 12 hr). Adenine nucleotide content, hepatic energy charge level, and ketone body ratio in the tissue were simultaneously measured, and they also decreased proportionally to the duration of preservation. There were close positive correlations between R×A and total adenine nucleotide concentration (r=0.841,P<0.01), between R×V and energy charge (r=0.787,P<0.01), and between R×V and tissue ketone body ratio (r=0.881,P<0.01). These results suggest that pyridine nucleotide fluorometry can accurately follow the cellular function of isolated porcine liver by administration of FC-43 in perfusate. This fluorometry may also have potential application in evaluating viability of a large organ like the human liver graft.