Abstract: Aim To study effects of Losartan on c-fos mRNA expression and free int racellular Ca²⁺([ Ca²⁺] i)level induced by AngiotensionⅡ(AngⅡ)in cardiomyocytes of neo natalrats.Methods Effect of Losartan on c-fos mRNA ex pression induced by AngⅡin cardiomyocytes was studied with dot blotting assay.Ca²⁺was measured with Ca²⁺sensitive fluorescent indicator (Fura-2/AM) using AR-C M-M IE cation measurement system.Results AngⅡtemporally induced c-fos gene expression and significantly increased the [Ca²⁺] ielevation in cardiomyocytes of neonatal rat s.However,the dynamic changes of c-fosgene expression and [Ca²⁺] i could be inhibited by Losartan 20μmol/L,but not by PD123319.Lo sartan 1~100μmol/L significantly inhibited AngⅡinduced [Ca²⁺] ielevation in adose-dependent manner.Conclusion The results suggest that c-fos expression and[Ca²⁺] ielevation induced by AngⅡare mediated by AT₁ subtype acceptor.Losartan maybe an effective drug in treating cardiac hypertrophy.

Key words: losartan, angiotension Ⅱ, c-fos proto-oncogene, Fura-2, cardiomy oocytes