Metabolism of xylitol and glucose in rats bearing hepatocellular.

The variation in metabolism of glucose and xylitol by diverse rat hepatocellular carcinomas and partially hepatectomized rat livers was studied. The AS-30D and FB56 tumors demonstrated a significantly different degree of utilization of glucose and xylitol in vitro. This correlated partially with the low activity of polyol dehydrogenase when xylitol was used as a substrate. The activity ofa nicotinamide adenine dinucleotide-dependent polyol dehydrogenase in various hepatomas ranged from nondetectable to 30 nmol/min/mg protein, with the lower activities in FB56 and AS-30D tumors at 0 and 0.22 nmol/min/mg, respectively; while nicotinamide adenine dinucleotide phosphate-dependent xylitol dehydrogenase activities ranged from 0 to FB56 to 3.31 nmol/min/mg protein in liver regenerated for 1 week. The activities of nicotinamide adenine dinucleotide phosphate-dependent enzyme for normal liver and AS-30D tumors measured 2.2 and 0.14 nmol/min/mg protein, respectively. Although only the 311C tumor had an activity equivalent to that of normal liver, the range of the nicotinamide adenine dinucleotide phosphate-dependent polyol dehydrogenase activities among the cell lines studies is narrow. The ratios of metabolites of [14C]glucose or [14C]xylitol were determined in rats bearing AS-30D tumors. Animals were given i.v. injections of a 10% solution of [14C]glucose or [14C]xylitol, 2 g/kg body weight. Assays of neutral sugar metabolites from each substrate in the acid-soluble fraction of liver or AS-30D tumor showed that xylitol in the liver was converted primarily into glucose while in the tumor 80 to 90% of the xylitol remained unchanged. This hepatocellular carcinoma is also markedly deficient in the ability to synthesize acid-insoluble glycogen and glycoprotein from xylitol as compared to the liver.