Effects of estrogen on composition and function of cardiac muscle

In vitro tension development is significantly reduced in surviving left ventricular columnae carneae and ATP treated glycerol extracted fibers of ovariectomized albino rats. This reduction in contractility is paralleled by decrease in ventricular actomyosin content. Heart-body weight ratio, myocardial water content and total protein concentration are not abnormal. No changes in excitability or refractoriness of surviving bundles of castrate animals were found. Treatment with alpha estradiol, 0.1 µg/day, returned tension production and actomyosin concentration to the normal range. It is concluded that the contractile system of cardiac muscle, like that of the uterus, is dependent on estrogen. These data suggest a general action of the hormone on contractile protein synthesis in all types of muscle and have important implications regarding cardiac and other muscular functions.