title: Hormonal regulation of translatable mRNA of tryptophan 2,3-dioxygenase in primary cultures of adult rat hepatocytes.
abstract: Tryptophan 2,3-dioxygenase [EC 1.13.11.11] in primary cultures of adult rat hepatocytes was induced 3-4 fold by 1 microM dexamethasone and 6-7 fold by dexamethasone plus glucagon (0.1 microM). Changes of the enzyme activity, amount of enzyme, measured by immunotitration, and rate of enzyme synthesis, assayed by measurement of [3H]leucine incorporation into the enzyme protein, were closely correlated. Furthermore, in a reticulocyte lysate system for cell-free protein synthesis, mRNA of the enzyme was translated to the protein corresponding to the subunit of tryptophan 2,3-dioxygenase, which was identified by SDS-polyacrylamide gel electrophoresis. The activity of translatable mRNA of the enzyme was increased more than 10-fold by dexamethasone and its final content in total mRNA was 0.34%. Glucagon alone did not increase mRNA activity, but dexamethasone plus glucagon increased mRNA activity to twice that with dexamethasone alone, the maximal content of the mRNA being 0.77% of the total mRNA content 12 h after addition of hormones. Insulin (0.1 microM) caused 75% inhibition of the maximum increase of mRNA activity of the enzyme induced by dexamethasone and glucagon. Epinephrine (10 microM) also caused 58% inhibition of the maximum increase. Insulin and epinephrine also suppressed increase of mRNA of tryptophan 2,3-dioxygenase induced by dexamethasone alone. Therefore, dexamethasone alone or together with glucagon stimulated transcription of tryptophan 2,3-dioxygenase increasing its mRNA and enzyme synthesis in hepatocytes. Conversely, insulin and epinephrine suppressed these increases of mRNA synthesis and thus decreased enzyme synthesis.
mesh_terms: D000818:Animals; D002474:Cell-Free System; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D004837:Epinephrine / Q000502:physiology; D005934:Glucagon / Q000502:physiology; D006728:Hormones / Q000502:physiology*; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D007328:Insulin / Q000502:physiology; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014366:Tryptophan Oxygenase / Q000235:genetics* / Q000378:metabolism
chemical_list: D006728:Hormones; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D007328:Insulin; D012333:RNA, Messenger; D003907:Dexamethasone; D005934:Glucagon; D014366:Tryptophan Oxygenase; D004837:Epinephrine