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Perfusion of livers from fasted rats with nitrogen-saturated buffer caused hepatocellular damage within 30 min. Lactate dehydrogenase (LDH) was released at maximal rates of approximately 300 U . g-1 . h-1 under these conditions, and virtually all cells in periportal and pericentral regions of the liver lobule were stained with trypan blue. Infusion of glucose, xylitol, sorbitol, or mannitol (20 mM) did not appreciably change the time course or extent of damage due to perfusion with nitrogen-saturated perfusate. However, fructose (20 mM) completely prevented damage assessed by LDH release, trypan blue uptake, and ultrastructural changes for at least 2 h of perfusion. Neither glucose, xylitol, sorbitol, nor mannitol (20 mM) increased lactate formation above basal levels during hypoxia. On the other hand, fructose (0.4-20 mM) caused a concentration-dependent increase in lactate formation that reached maximal rates of approximately 180 mumol . g-1 . h-1. The dose-dependent increase in glycolytic lactate production from fructose correlated well with cellular protection reflected by decreases in LDH release. ATP:ADP ratios were also increased from 0.4 to 1.8 in a dose-dependent manner by fructose. The results indicate that fructose protects the liver against hypoxic cell death by the glycolytic production of ATP in the absence of oxygen.

The protective effect of N-acetylcysteine against the toxicity of paracetamol, acrolein, and paraquat was investigated using isolated hepatocytes as the experimental system. N-acetylcysteine protects against paracetamol toxicity by acting as a precursor for intracellular glutathione. N-acetylcysteine protects against acrolein toxicity by providing a source of sulfhydryl groups, and is effective without prior conversion. Paraquat toxicity can be decreased by coincubating the cells with N-acetylcysteine, but the mechanism for the protective effect is not as clear in this instance. It is probable that N-acetylcysteine protects against paraquat toxicity by helping to maintain intracellular glutathione levels.

Viability, glycolytic capacity and energy metabolism under anaerobic conditions were studied in the hepatoma cell lines HTC, FU5 and HepG2 and in rat and human hepatocytes using glucose and fructose as glycolytic precursors. During 6 hr of anaerobic incubation without additional substrate, viability decreased rapidly in FU5 and HTC cells, whereas viability of HepG2 cells was not significantly affected. In all tumor cells, 10 mmol/L glucose prevented hypoxic cell injury almost completely. Lactate formation from glucose was about five times higher than in hepatocytes under these circumstances. ATP content of the tumor cells remained almost constant under anaerobic conditions in the presence of glucose. Ten millimoles per liter of fructose diminished glycolysis in the hepatoma cells compared with glucose, ranging from 87% reduction in HTC cells to 43% reduction in HepG2 cells. Accordingly, ATP content decreased rapidly in the FU5 and slowly in the HepG2 cells. Viability was strongly diminished in the HTC and FU5 cells in the presence of fructose, whereas in the HepG2 cells no effect of fructose on viability was detectable. In contrast to the hepatoma cells, rat and human hepatocytes exhibited higher rates of anaerobic glycolysis in the presence of fructose and thus were able to maintain their viability under these conditions. These differences in glycolytic capacity, energy metabolism and hypoxia tolerance of hepatoma cells compared with hepatocytes may be used for the treatment of liver cancer by isolated liver perfusion and ex situ revision of the organ.