The Difference Of RyR2 And Redox Status In Heart Between Exercise And Hyperthyroidism

Backgrounds: Both Thyroid hormone and exercise had an effect on inducing cardiomyocyte hypertrophy and oxidative stress to the mammalian heart in the adult, with the change of Glutathione Peroxidase(GPx); however, there were a lot of distinct difference in the procedure between them. As we had known, the reserve capacity of heart would be increasingly improved. Thyroid hormone imbalance might lead to the remodeling procedure process and cardiac failure. The distinguish in heart between function and morphology could be mediated by various signal pathway or molecular mechanisms such as the expression level of relative protein and the status of ion channel. Burgoyne found that Ryanodine Receptor 2(Ry R2) repressed cardiomyocyte which were a series of reactions induced by ion channel activation and increased frequency to achieve growth and proliferation in the adult mammalian, which was mainly induced by Ry R2. The proliferation was regulated, at least, by the reduadant reactive oxygen species. Besides, rats with decreased cardiac Ry R2 levels showed resistance to cardiac failure when pressure overload to a certain degree.Objectives: To probe the major discrepancy and likenesses of Ry R2 m RNA or protein level and redox status hypertrophy animal models caused by thyroid hormone or exercise.Methods: Rats were randomly separated into 6 groups, which were control,mild hyperthyroidism, severe hyperthyroidism, furthermore, each group was randomly divided into 2 groups, namely exercise and nonexercise. The mild hyperthyroidism model and severe hyperthyroidism model rats were given 100μg/d Levo-Thyroxine(L-T4), and 200μg/d L-T4 each. Swimming training model rats were given 30min/d with the burdens of 6% of the body weight. When rats were administred for fourteen days, the listed parameters were gauged, namely the morphology and function of thyroid and cardiac, the status of oxidative stress(GPx activity, Malondialdchyde(MDA) content), the expression of Ry R2 m RNA and Ry R2 protein.Results:1. After given different dosage of thyroid hormone, the smaller thyroid, the higher FT3, and patholo-gical cardiac remodeling were found in rat.2. Given by Levo-thyroxine, whether exercise or not, MDA content were higher than those of control group.4. Compared with the non-exercise group, both GPx activity and MDA content inexercise group were higher.5. No difference was found in the expression of Ry R2 m RNA, however, the expression of Ry R2 protein was lower in hyperthyroidism group.Conclusion: Thyroid hormone was harm to the expression of Ry R2, the homeostatic of redox, which could be recovered to some extent by moderately exercise.