title: Early molecular events in rat heart after administration of triiodothyronine and isoproterenol.
abstract: Triiodothyronine (T3), isoproterenol and aminophylline injected daily into rats induce heart hypertrophy. We have compared the early effects of a single injection of each of these compounds to rats using myocardial RNA synthesis and translational efficiency. In rats injected with T3 4 h before death the synthesis of RNA was increased 2-fold, then the effect of T3 injection decreased with time. Injection of isoproterenol had no effect. Injection of T3 increased the amount of myocardial polysomes, heavy polysomes appeared approx. 15 h after the injection. Neither isoproterenol nor aminophylline modified the polysomal pattern. RNAs were translated in reticulocyte lysates in the presence of [35S]methionine. A small but significant increase in incorporation was observed with RNAs from rats injected with T3 4 and 18 h before death, whereas no modification were observed with RNAs from isoproterenol- and aminophylline-treated rats. Two-dimensional electrophoresis and radioautography showed significant qualitative and quantitative differences between the translational products of RNAs from control, T3-, isoproterenol- and aminophylline-injected rats. These observations are compatible with a mechanism of action of T3 at the transcriptional level and of cAMP on the processing and/or on the stability of various RNA species.
mesh_terms: D000818:Animals; D006332:Cardiomegaly / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D007545:Isoproterenol / Q000633:toxicity*; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D011061:Poly A / Q000235:genetics; D011132:Polyribosomes / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects*; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger; D051381:Rats; D011919:Rats, Inbred Strains; D014158:Transcription, Genetic / Q000187:drug effects*; D014284:Triiodothyronine / Q000633:toxicity*
chemical_list: D012333:RNA, Messenger; D014284:Triiodothyronine; D011061:Poly A; D012313:RNA; D007545:Isoproterenol