Objective:To investigate the effects of sodium tanshinoneⅡA sulfonate(STS)on the hypertrophy induced by angiotensinⅡ(AngⅡ)in primary cultured neonatal rat cardiac myocytes. Methods:The effect of STS on cytotoxicity was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-3,5- phenytetrazoliumromide(MTT)assay.As indexes for cardiocyte hypertrophy,cell size was determined by phase contrast microscopy and protein synthesis rate was measured by ~3H-leucine incorporation. The proto-oncogene c-fos mRNA expression of cardiocytes was assessed using reverse transcription polymerase chain reaction(RT-PCR).Results:STS could inhibit cardiocyte hypertrophy,increase the protein synthesis rate,and enhance proto-oncogene c-fos mRNA expression in cardiocytes induced by AngⅡ(P<0.01),with an effect similar to that of Valsartan,the AngⅡreceptor antagonist.Conclusion:STS can prevent the hypertrophy of cardiac myocytes induced by AngⅡ,which may be related to its inhibition of the expression of proto-oncogene c-fos mRNA.