Effect of Branched-Chain Amino Acids on Albumin Gene Expression in the Liver of Galactosamine-Treated Rats

Abstract

Acute liver injury was induced in rats by the administration of galactosamine, which brought about inhibition of RNA synthesis and protein synthesis in the liver. The galactosamine-treated rats were infused with total parenteral nutrition solutions containing various proportions of branched-chain amino acids and the recovery from the galactosamine intoxication was followed by measuring albumin mRNA levels and polysome profiles. The levels of total cytoplasmic albumin mRNA were markedly decreased on day 2 after the galactosamine treatment, but the levels were restored to almost the control value by day 4 in all the groups irrespective of the content of branched-chain amino acids in the infusion solutions. On the contrary, the levels of β-actin mRNA changed in the opposite direction to those of albumin mRNA. It was also found that polysomes in the liver were extensively disaggregated on day 2 after the galactosamine treatment, but the polysome profiles returned to normal on day 4 in all the groups. However, when the levels of polysome-associated albumin mRNA were quantitated, we found that the extent of the recovery was dependent on the content of branched-chain amino acids in the infusion solutions; as the content of branched-chain amino acids increased, the level of polysome-associated albumin mRNA increased. These results suggest that the integration of albumin mRNA into functional polysomes in the liver is regulated by the supply of branched-chain amino acids.