EFFECT OF BRANCHED-CHAIN AMINO-ACIDS ON ALBUMIN GENE-EXPRESSION IN THE LIVER OF GALACTOSAMINE-TREATED RATS

Acute liver injury was induced in mts by the administration of galacto samine, which brought about inhibition of RNA synthesis and protein sy nthesis 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 in toxication was followed by measuring albumin mRNA levels and polysome profiles. The levels of total cytoplasmic albumin mRNA were markedly d ecreased on day 2 after the galactosamine treatment, but the levels we re restored to almost the control value by day 4 in all the groups irr espective of the content of branched-chain amino acids in the infusion solutions. On the contrary, the levels of beta-actin mRNA changed in the opposite direction to those of albumin mRNA. It was also found tha t polysomes ill the liver were extensively disaggregated on day 2 afte r the galactosamine treatment, but the polysome profiles returned to n ormal 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 aci ds in the infusion solutions; as the content of branched-chain amino a cids increased the level of polysome-associated albumin mRNA increased . These results suggest that the integration of albumin mRNA into func tional polysomes in the liver is regulated by the supply of branched-c hain amino acids. (C) Elsevier Science Inc. 1998.