Objective    To explore the mechanism by which urotensin Ⅱ induces hypertrophy of the cultured rat cardiomyocytes.     Methods    The cultured cardiomyocytes from neonatal SD rats were treated with urotensin Ⅱ

also with cyclosporine A for its blocking effect on urotensin Ⅱ induced cardiomyocytes hypertrophy. The mRNA and protein levels of β-MHC and CaN were evaluated by real-tim

e PCR and Western blotting

respectively.     Results    In the cells treated with 10

-8

and 10

-7

mol/L urotensin Ⅱ

the mRNA and protein levels of β-MHC and CaN were significantly higher than that of control (

P

<

0.05). Treatment of cardiomyocytes with 10

-8

mol/L urotensin Ⅱ for 12-48 h induced a time-dependent increase of β-MHC and CaN mRNA and protein expressions (

P

<

0.05). Urotensin Ⅱ-induced upregulation of β-MHC and CaN mRNA and protein expressions can be abated by 24-hour cyclosporine A pretreatment (

P

<

0.05).     Conclusion    Urotensin Ⅱ can induce cardiomyocytes hypertrophy and cyclosporine A can block this effect. CaN participates in this process. Our results may contribute to the investigation of cardiaomyocyts hypertrophy induced by hypertension and other cardiac diseases.