CALL FOR PAPERS Sex Steroids and Gender in Cardiovascular-Renal Physiology and Pathophysiology Effects of voluntary wheel running on cardiac function and myosin heavy chain in chemically gonadectomized rats

Hydock DS, Lien C-Y, Schneider CM, Hayward R. Effects of voluntary wheel running on cardiac function and myosin heavy chain in chemically gonadectomized rats. Am J Physiol Heart Circ Physiol 293: H3254–H3264, 2007. First published September 28, 2007; doi:10.1152/ajpheart.00801.2007.—Reducing testosterone and estrogen levels with a luteinizing hormone-releasing hormone agonist such as Zoladex (i.e., chemical gonadectomy) is a common treatment for many prostate and breast cancer patients, respectively. There are reports of surgical gonadectomy inducing cardiac dysfunction, and exercise has been shown to be cardioprotective under these circumstances. Minimal research has been done investigating the effects of chemical gonadectomy and increased physical activity on cardiac function. The purpose of this investigation was to examine the effects of chemical gonadectomy and physical activity on cardiac function. Male (M) and female (F) Sprague-Dawley rats received either Zoladex treatment (Zol) that suppressed gonadal function for 8 wk or control implants (Con) and either were allowed unlimited access to voluntary running wheels (WR) or remained sedentary (Sed) throughout the treatment period. In vivo and ex vivo left ventricle (LV) function were then assessed, and myosin heavy chain (MHC) expression was analyzed to help explain LV functional differences. Hearts from M Sed Zol exhibited significantly lower aortic blood flow velocity, developed pressure, and maximal rate of pressure development and higher -MHC expression than M Sed Con. Hearts from F Sed Zol exhibited significantly lower LV wall thicknesses, fractional shortening, and developed pressure and higher -MHC expression than F Sed Con. This cardiac dysfunction was not evident in hearts from M or F WR Zol, and this was associated with a preservation of the MHC isoform distribution. Thus an 8-wk chemical gonadectomy with Zoladex promoted cardiac dysfunction in male and female rats, and voluntary wheel running protected against this cardiac dysfunction.