Effects of Chronic treatment with Losartan on Cardiac Extracellular Matrix in Spontaneously Hypertensive Rats

Objective:To investigete chronic treatment with angiotensionⅡ type 1 receptor antagionist losartan reverses left ventricular fibrosis in SHR. Methods:This study was performed in 33 week old Wistar kyoto(WKY)rats(\%n\%=8), SHR(\%n\%=6), and SHR treated with losartan(30 mg/kg per day)for 17 weeks(\%n\%=6).Blood pressure,Cardiac mass,left ventricular mass and left ventricular mass index were measured.Cardial total collagen was stained with Van Gieson methold.Collage volume fraction was determined in the left ventricle by quantitative morphometry. Collagen Ⅲ stained by immunohistochemistry was evaluated with scoring.Cardiac extracellular matrix was observated with eletromicroscope and the numbers of fibroblasts in left ventricle were calculated. Results:Compared with WKY rats, SHR exhibited increased BP, left ventricular mass,left ventricular collagen volume fraction,left ventricular collagen Ⅲ, and the numbers of cardiac fibroblast(\%P\%0 05 respectively). After the treatment treated SHR showed no left ventricular hypertrophy and diminished the high BP(\%P\%0 05). Left ventricular collagen volume fraction and collagen Ⅲ dereased in treated SHR then in untreated SHR,but no changes in numbers of fibroblast were observed between treated SHR and untreated SHR. Conclusion:Chronic treatment with losartan can normalized blood pressure and reversed left ventricular hypertrophy in SHR,significantly inhibited collagen compositions in left ventricle. But it cannot inhibit proliferation of cardiac fibreblasts in SHR.