Posttranscriptional control in the steroid-mediated induction of hepatic tyrosine transaminase.

The purine analog azaguanine does not inhibit the initial induction of hepatic tyrosine transaminase by hydrocortisone. However, the continued induced synthesis of tyrosine transaminase, elicited by repeated doses of hydro-cortisone, is inhibited approximately 64 percent in the presence of the analog after 7 to 8 hours and appears to be almost completely inhibited by 9 to 10 hours; this suggests that the induction cycle involves the activation and renewal of a pool of preexisting messenger RNA.