Modulation of albumin gene expression by amino acid supply in rat liver is mediated through intracellular concentration of pyridoxal 5′-phosphate

• Published in: The Journal of nutritional biochemistry 1997-04, Vol.8 (4), p.211-216
• Main Authors: Oka, Tatsuzo, Kuwahata, Masashi, Sugitatsu, Hitomi, Tsuge, Haruhito, Asagi, Kozo, Kohri, Hideaki, Horiuchi, Saburou, Natori, Yasuo
• Format: Article
• Language: English
• Subjects: albumin; amino acids; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; gene expression; Liver. Bile. Biliary tracts; pyridoxal phosphate; rat liver; Vertebrates: digestive system
• ISSN: 0955-2863; 1873-4847
• DOI: 10.1016/S0955-2863(97)00006-5

Rats were nourished by infusion of total parenteral nutrition solutions containing 0% or 3.3% amino acids for 7 days. The level of albumin mRNA in the liver of amino acid-infused rats was found to be several fold higher than that in the liver of amino acid-depleted rats. Expression of albumin gene is known to be regulated by tissue-specific transcription factors such as HNF-1 and C EBP . We determined the binding activities of liver nuclear extracts to the HNF-1- and C EBP -binding sites by gel mobility-shift assay and found that the activities of the extract prepared from liver of amino acid-infused rats were greater than those of amino acid-depleted rats. In view of our recent finding that vitamin B 6 modulates albumin gene expression through inactivation of tissue-specific transcription factors by direct interaction with pyridoxal phosphate, we determined the intracellular concentrations of vitamin B 6 derivatives. We found that the concentration of pyridoxal phosphate in the liver of amino acid-infused rats was decreased to almost half of that of amino acid-depleted rats, whereas the concentration of pyridoxamine phosphate was increased in the opposite direction. These observations suggest that an increase in albumin mRNA level in the liver of amino acid-infused rats may be caused by a decrease in intracellular concentration of pyridoxal phosphate, which in turn relieves inactivation of tissue-specific transcription factors.