Aim:To investigate the possible roles of peroxisome proliferator-activated recep-tor α(PPARα) and the signal pathway regulating the transcription of PPARα inthe cardiomyocyte differentiation course of murine embryonic stem (ES) cells invitro.Methods:The expression of PPARα during cardiomyocyte differentiationwas analyzed using both Western blotting and immunofluorescence.Cardiacspecific genes and sarcomeric proteins were evaluated when embryoid bodieswere challenged with PPARα specific inhibitor GW6471 at different time courses.The phosphorylation of p38 mitogen-activated protein kinase (MAPK) was stud-ied in the differentiation process,and its specific inhibitor SB203580 was em-ployed to study the function of p38 MAPK on cardiac differentiation and theexpression of PPARα.Results:The expression of PPARα was observed to be ata low level in undifferentiated ES cells and markedly induced with the appearanceof beating clusters.The inhibition of PPARα by its specific inhibitor GW6471(1×10~(-5) mol/L) significantly prevented cardiomyocyte differentiation and resultedin the reduced expression of cardiac sarcomeric proteins (ie α-actinin,troponin-T)and specific genes (ie α-MHC,MLC2v) in a time-dependent manner.In the differ-entiation course,p-p38 MAPK was maintained at a high level from d 3 followed bya decrease from d 10.The inhibition of the p38 MAPK pathway by SB203580between d 3 and d 7 efficiently prevented cardiomyocyte differentiation and re-suited in the capture of the upregulation of PPARα.Conclusion:Taken together,these results showed a close association between PPARα and cardiomyocytedifferentiation in vitro,and p38 MAPK was partly responsible for the regulationof PPARα. Aim: To investigate the possible roles of peroxisome proliferator-activated recep-tor α (PPARα) and the signal pathway regulating the transcription of PPARα inthe cardiomyocyte differentiation course of murine embryonic stem (ES) cells invitro. Methods: The expression of PPARα during cardiomyocyte differentiationwas analyzed using both Western blotting and immunofluorescence.Cardiacspecific genes and sarcomeric proteins were evaluated when embryoid bodieswere challenged with PPARα specific inhibitor GW6471 at different time courses. The phosphorylation of p38 mitogen-activated protein kinase (MAPK) was stud-ied in the differentiation process , and its specific inhibitor SB203580 was em-ployed to study the function of p38 MAPK on cardiac differentiation and theexpression of PPARα. Results: The expression of PPARα was observed to be at low level in undifferentiated ES cells and markedly induced with the appearance of beating clusters . The inhibition of PPARα by its specific inhibitor GW647 1 (1 × 10 -5 mol / L) highly prevented cardiomyocyte differentiation and resulted in the reduced expression of cardiac sarcomeric proteins (ie α-actinin, troponin-T) and specific genes (ie α-MHC, MLC2v) time-dependent manner.In the differ-entiation course, p-p38 MAPK was maintained at a high level from d 3 followed bya decrease from d 10. The inhibition of the p38 MAPK pathway by SB203580between d 3 and d 7 efficiently prevented cardiomyocyte differentiation and re-suited in the capture of the upregulation of PPARα. Confoc: Taken together, these results showed a close association between PPARα and cardiomyocystifferentiation in vitro, and p38 MAPK was partly responsible for the regulation of PPARα.