Cycloheximide Causes Increased Accumulation of Translatable mRNA for Tyrosine Aminotransferase and Tryptophan Oxygenase in Livers of Cortisol‐Treated Rats

Publisher Website
Google Scholar
Abstract
MRNA activities for 2 cortisol-inducible enzymes, tyrosine aminotransferase and tryptophan oxygenase, were determined by translation in a wheat germ system. The effects of cycloheximide on the 2 mRNA activities were evaluated. Cortisol leads to an increase of the translatable mRNA for tyrosine aminotransferase and tryptophan oxygenase with a maximum at approximately 6 h. Cycloheximide was administered 4 h after treatment with cortisol; 2 h later, the activities of tyrosine aminotransferase and tryptophan oxygenase mRNA had increased 5-fold and 2-fold, respectively, compared to the activities reached with cortisol alone. Thereafter the amount of the 2 translatable mRNA declined, though 14 h after cortisol administration the mRNA activities were still severalfold higher than in control animals. Application of .alpha.-amanitin together with cycloheximide did not prevent an increased accumulation of specific translatable mRNA. The increase in tyrosine aminotransferase and tryptophan oxygenase activity by cortisol was immediately blocked by cycloheximide. Whereas tryptophan oxygenase activity rapidly declined after cycloheximide application, tyrosine aminotransferase activity remained at the same level. Approximately 4 h thereafter, both enzyme activities increased again.