The effects of galactosamine on UTP levels in the livers of young, adult and old rats

Galactosamine (GalN), a well-known hepatotoxin that depletes the cellular p ool of uracil nucleotides, was previously shown to have greater impact on t he inhibition of protein synthesis in hepatocytes of old rats as compared w ith young animals (Kmiec 1994, Ann. N.Y. Ac. Sci. 717, 216-225). In the pre sent study we compared the effects of GalN on the nucleotide content (measu red by ion-exchange HPLC) in the livers of young (4 months), adult (12 mont hs), and old (24-26 months old) rats two hours after its intraperitoneal ad ministration. UTP content of the Livers of old control rats was significant ly lower (by 28%) than that of young animals. GalN administration decreased the UTP content in the livers of young, adult and old rats by, respectivel y, 55%, 65% and 89%, and increased the content of UDP-sugars by 189%, 175% and 305%. The hepatic content of ATP, ADP, AMP, NAD, GTP except CTP did not differ significantly among the age groups of rats studied, and was not cha nged by GalN treatment. The content of CTP was significantly higher in old rats (P < 0.03) upon GalN treatment. The lower hepatic content of UTP may p artially explain the increased sensitivity of hepatocytes and livers of old rats to the action of galactosamine, and possibly to other hepatotoxic com pounds that decrease transcription in the liver.