The Difference Of C/EBPβ MRNA And Redox Status Between Physiological And Pathological Hypertrophy

Backgrounds:Both exercises and thyroid hormone can induce oxidative stress and cardiomyocytes hypertrophy in the adult mammalian heart; however, the results were often extent different. As we had known, moderate exercises were conducive to better compensatory ability against stress; however, the heart inclined to pathological cardiac remodeling or cardiac failure under the stress of thyroid hormone. That is to say, the former was a physiological process, but the latter was a pathological process. The discrepancy between morphology and function of heart might be mediated by diverse pathophysiological process or molecular mechanisms. Bostrom found that C/EBPP repressed cardiomyocyte growth and proliferation in the adult mammalian heart and that reduction in C/EBPP was a central signal in physiological hypertrophy and proliferation. This proliferation was mediated, at least in part, by the increased CITED4. Furthermore mice with reduced cardiac C/EBPβ levels displayed substantial resistance to cardiac failure upon pressure overload.Objectives:To explore the main differences and similarities of C/EBPβ mRNA level and redox status between experimental physiological and pathological hypertrophy animal model which be achieved by moderate exercise or levo-thyroxine sodium.Methods:Wistar rats were randomly divided into8groups, which were control I, mild hyperthyroidism (MT), severe hyperthyroidism (HT) and hypothyroidism (L), furthermore, each group were divided into two groups, or exercise and no exercise. The model of mild hyperthyroidism (MT), severe hyperthyroidism (HT) and hypothyroidism (L) rats were established by giving100μg/d levo-thyroxine,200μg/d levo-thyroxine and l0mg/d methimazole respectively. Swimming training was done for30min/d under the burden of6%of the body weight. After administration for14 days, the following parameters were measured, i.e. the morphology and function of thyroid and cardiac, the status of oxidative stress (H2O2content, GPx activity, SOD activity and MDA content) and the expression of C/EBPP mRNA and CITED4mRNA.Results:1. After administration for14d, the content of colloid in thyrocytes and the level of thyroid hormones in serum were higher in levo-thyroxine group than those of control group, however, the two indexes were lower in methimazole administration group. The above changes were partly reversed to normal status by exercise.2. Both well-organized collagen fibers and adequate supply of bloodstream were found in the exercise group; however, pathological cardiac remodeling and insufficiency in blood were found in both levo-thyroxine and methimazole groups.3. Given by levo-thyroxine, whether exercise or not, MDA content was higher. However, given by methimazole, MDA content was higher only in exercise. Furthermore, GPx activity and SOD activity were higher in hypothyroidism group whether exercise or not. Given by levo-thyroxine or methimazole, except SOD activity was lower, all of H2O2content, GPx activity and MDA content index were higher in exercise group than those of without exercise group, however, no difference was found in MDA content between exercise group and control group.4. There was no difference in the expression of C/EBPβ mRNA and CITED4mRNA.Conclusion:Moderate exercise or levo-thyroxine may induce entirely different myocardial hypertrophy; furthermore, moderate exercises may partly antagonize the biological effect of thyroid hormone during the occurrence and progress of myocardial hypertrophy. There was no obvious oxidative damage to heart in rats after administration by moderate exercise, however, exercise and hyperthyroidism, exercise and hypothyroidism, and hyperthyroidism would induce oxidative damage.