The Effect Of Iodine Deficiency And Iodine Excess On The Expression Of Rat Myocardial Myosin Heavy-chain Gene MRNAs

Iodine is an essential trace element for synthesis of thyroid hormone (TH). Under the condition of iodine either deficiency or excess, synthesis of TH will be affected. TH plays important roles in regulation of organic functions, such as brain development, bone growth, cardiac contraction. As a target of TH, the expression of myocardial myosin heavy-chain (MHC) genes in the heart is influenced by the level of TH. Myocardial myosin, a kind of cardiac contractile protein, consists of two heavy chains, α-myosin heavy-chain (α-MHC) and β- myosin heavy-chain (β-MHC). There are different levels of ATPase enzymatic activity located in the heavy chain of the myosin molecules. The ATPase of the heavy chains of a-isoform acts is more active than that of the heavy chain of β-isoform, thus increasing contractility. It has been know that the expression of cardiac MHC marked regulated by TH. However, the effects of long term iodine deficiency and iodine excess on the expression of myocardial myosin heavy-chain are unknown so far.