Heat shock protein expression in the myocardium of Fischer 344 rats after endurance training

Heat shock proteins (HSP) are expressed after cells are exposed to various types of stress and may provide protection against cellular insult. Previous data have shown increases in HSP expression following exhaustive exercise; however, it is not known if chronic exercise will increase resting levels of HSP. The purpose of this study was to determine if HSP 60 and 72/73 increased in the myocardium of endurance trained Fischer 344 rats. Hearts were sectioned into left ventricle (LV), right ventricle (RV) and atria (AT). 16-20 weeks of endurance training improved myocardiai oxidative metabolism (P<0.05) as shown by increases of 88%, 90% and 77% in citrate synthase activity of LV, RV and AT, respectively. Cardiac muscle proteins were separated by SDS-PAGE and immunoblotted for HSP 60 and 72/73. HSP 72/73 expression was significantly greater (P<0.05) in endurance trained versus control rats in the LV, RV, and AT (20%, 62% and 70%, respectively). LV HSP 60 increased 43% (P<0.05) in trained relative to control rats. HSP 60 was unchanged in RV and AT after training. These results indicate that endurance training increases the expression of stress proteins and is consistent with the hypothesis that endurance training may provide a protective mechanism to stress.