Early molecular events in rat heart after administration of triiodothyronine and isoproterenol.
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.
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*
D012333:RNA, Messenger; D014284:Triiodothyronine; D011061:Poly A; D012313:RNA; D007545:Isoproterenol