Myocardial energy metabolism is an important determinant of cardiac structure and function. The peroxisome proliferator-activated receptor family of nuclear receptor transcription factors is an important regulator of cardiac metabolism. The PPARs control myocardial metabolism by transcriptionally regulating genes encoding enzymes involved in fatty acid and glucose utilization. The expression and activity of the PPARs and coactivator protein PGC-1α in cardiomyopathic and metabolic diseases had been studied. however, little is documented regarding their role in the exercise trained heart. The present study was to investigate the expression of PPARɑ and coactivator protein PGC-1α in left ventricles in different training status so as to understand its role in the regulation of lipid and lipoprotein metabolism in trained heart. METHODS: Male 8-week-old Sprague-Dawley rats were randomly divided into either exercise training or control groups. The exercise training groups were subjected to a single bout of exercise, 4-week or 10-week exercise training respectively according to our previously exercise training protocols, and then rats were decapitated at 0h, 3h and 24 hour after last exercise. The heart was weighed, and then tissues of left ventricle were frozen for determination of the proteins by Western blotting analysis. RESULTS: A single bout of exercise induced a transient increase in the expression of PPARɑ( 0h vs 24h, p<0.05), while the acute exercise induced a prolonged significant increase in the expression of PGC-1α immediately after a single bout of exercise in untrained rats( Con vs 0h, p<0.05; Con vs 3h, p<0.01; Con vs 24h, p<0.05), however, after 4 weeks of training, no significant change in the expressions of PPARɑ and PGC-1α were observed either in the basal level or in response to acute exercise in 4-week trained and 10-week trained rats. CONCLUSION: The expression of the PPARα and it coactivator protein PGC-1α is dynamically regulated by a single bout of exercise, which indicated that PPARα and it coactivator protein PGC-1α is involved in the regulation of myocardial energy metabolism, however, after incremental exercise training, the PPARα and their coactivator protein PGC-1α might not play important role in the regulation of myocardial energy metabolism, the mechanism underling this change need to be further studied.