title: Isomyosin and thyroid hormone levels in pressure-overloaded weanling and adult rat hearts.
abstract: We examined the relationship between ventricular isomyosin composition and plasma thyroxine (T4) 5 wk after partial constriction of the abdominal aorta in weanling (21 day) and adult (8 wk) rats. Cardiac enlargement in weanling aorta-constricted animals was associated with a significant (P less than 0.001) decrease in %V1 isomyosin in both left (32%) and right ventricles (25%) with a corresponding increase in the %V3 isomyosin and a reduction in plasma T4 levels. However, the ratio of V1/T4 was similar in weanling control (17.8 +/- 0.8) and aorta-constricted (18.0 +/- 1.4) rats. In adult aorta-constricted animals, there was a significant (P less than 0.001) reduction in the %V1 (16%) isomyosin in the left ventricle and a smaller decrease in the right ventricular V1 (8%) with no change in plasma T4 levels. There was also a significant difference in V1/T4 between control (16.1 +/- 0.4) and aorta-constricted (13.9 +/- 0.7) adult rats in contrast to the maintenance of the V1/T4 in weanling aorta-constricted animals. Thus both increased workload and changes in thyroxine levels contribute to the isomyosin redistribution seen in weanling rats subjected to a pressure overload, whereas, in adult hypertrophied hearts, alterations of the ventricular isomyosin composition appear to be due solely to the increased pressure overload.
authors.forename: A F
authors.initials: AF
authors.lastname: Martin
authors.forename: D C
authors.initials: DC
authors.lastname: Robinson
authors.forename: R T
authors.initials: RT
authors.lastname: Dowell
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000601:surgery; D001794:Blood Pressure; D006332:Cardiomegaly / Q000378:metabolism* / Q000503:physiopathology; D003250:Constriction; D004591:Electrophoresis, Polyacrylamide Gel; D006321:Heart / Q000503:physiopathology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000503:physiopathology; D013974:Thyroxine / Q000097:blood*; D014886:Weaning
chemical_list: D009218:Myosins; D013974:Thyroxine