Background Angiotensin Ⅱ(Angll) and platelet-derived growth factor(PDGF)-BB can induce hypertrophy in the cultured rat cardiomyocytes through different signal transduction pathways.Angll stimulates growth lhrough G protein coupled receptor(GPCR),while PDGF-BB acts via receptor tyrosine kinase(RTK).Although there has been much development On the individual Angll and PDGF-BB mediated signal pathways,little is known about the interactions between these two factors-Therefore,the crosstalk between Angll and PDGF.BB mediated signal pathways in the rat cardiomyocytes was investigated in this study.Metnods Primary culture of neonatal rat ventricular myocytes was prepared.The amount of tyrosine-phosDhorylated and non-phosphoryiated PDGF-β receptor,Gαq/11,and phospholipase C(PLC)β3 were measured by immunoblotting analysis. The statistical analysis was done by one-way ANOVA.Results Fyrosine-phosphorylated PDGF-β receptor was increased by 120.60% at 1 minute and recovered to the control level at 10 minutes after Angll stimulation.Phosphorylation of PDGF-β receptor triggered by Angll was blocked by losartan, a specific antagonist of AT1 receptor.PLC inhibitor U73122,protein kinase C(PKC)inhibitor staurosporine(STS) and mitogen-activated ERK activating kinase(MEK) inhibitor PD98059 also inhibited the Angll-induced phosphorylation of PDGF-β receptor.PDGF-BB slightly increased the expression of Gαq/11 protein.Conclusion Angll transactivates PDGF-β receptor via AT1 receptor-Gαq/11-PLC-PKC pathway in the rat cardiomyocytes.ERK also participates in the transactivation of PDGF-β receptor triggered by Angll.