Liver haemodynamics were studied after warm (37 °C) ischaemia of isolated rat livers for periods of 30 s (Group 1), 30 min (Group 2), and 60 min (Group 3) using a constant pressure system with a recirculating blood-free perfusate. Portal flow recovered to basal values within 6 min in livers from Group 1, whereas it was significantly reduced in Group 2 during the initial 15 min and in Group 3 during the first 33 min of reperfusion. Thus, the recovery of liver flow was proportional to the duration of ischaemia. By using the same mode of liver perfusion, the effect of norepinephrine on portal resistance was also studied in normal livers. At the beginning of reperfusion, the values of portal resistance in ischaemic livers were comparable to the values of portal resistance mediated by norepinephrine at concentrations between 10“7 and 10"6 mol/1 in normal livers. The results suggest that vasoconstriction of the hepatovasculature may be a contributing factor to the reperfusion injury of the liver following warm ischaemia.
The uptake, reflux and excretion of bromosulfophthalein (BSP) were studied on a model of total warm ischaemia for 30 min (group 1) or 60 min (group 2) followed by reperfusion for 45 min in the isolated perfused rat liver of unfasting rats. In group 1, the BSP hepatic uptake was comparable to control livers (30 s ischaemia plus 45 min reperfusion), but was significantly reduced in group 2. The reflux of BSP from liver to perfusate in group 1 and group 2 resulted in the appearance of secondary concentration time peaks of BSP in the reservoir perfusate. This result suggests that ischaemia-reperfusion induced a qualitative change in BSP pharmacokinetics. Excretion of the dye into bile was significantly impaired in group 2 only. The leakage of lactate dehydrogenase into the perfusate was increased moderately in both group 1 and group 2 in comparison to the controls, suggesting a low degree of liver parenchymal injury. In conclusion, the results of this investigation showed that BSP pharmacokinetics were not only undergoing quantitative changes but also a qualitative change in the model of ischaemia-reperfusion injury of the liver obtained from fed rats and may thus serve as a highly sensitive indicator of liver viability.