Introduction: Endurance activity has a significant influence on remodeling of the heart, such as MHC protein, on otherhand,Pur&beta is mediator of repression of &betaMHC gene expression and decrease of its expression, the purpose of this study was to investigate the effects of endurance training on Pur&beta gene expression in the heart of trained wistar male rats. So the aim of this study was to investigate the effect of endurance training on Pur&betagene expression in left ventricle.

Materials & methods: For this purpose, 14 rats under controlled conditions (temperature, light/dark (12:12) cycle, with ad Libitum access to food and water) were housed and randomly assigned to control and experimental groups, the experimental group performed 14 weeks endurance exercise on motorized treadmill, and then 48 hours after the end of the last session were anesthetized as sacrificed. The left ventricle of the heart was removed. Real time RT-PCR method was used to determine the expression levels of Pur&betain the left ventricle. Finally, the obtained data were evaluated using t-test.

Findings: The results of this research showed, physical activity not only influence on m-mode indices and heart weigh, but also it enhance weight and internal dimensions of heart which is coincide with the significantly decrease Pur&betagene expression.

Discussion & Conclusions: Given to the different effects of endurance activities in the size of the heart And Pur&beta gene expression and also Pur&beta role on type &alpha of MHC isoform expression, it seems that  heart mass changes due to physical activities is related to type &alpha of MHC isoform.