Effects of Losartan and Captopril on Myocardial Fibrosis in Spontaneously Hypertensive Rats

Objective To investigate the change of myocardial fibrosis in spontaneously hypertensive rats(SHR) by inhibition the renin angiotensin system in different level. Methods Twenty nine males SHR (15 weeks old) were divided into four groups: SHR control group(SHR15W, n =7; SHR30W, n =8); Losarton group(SHRLos, n =7); Captopril group (SHRCap, n =7); Wistar kyoto(WKY) control group(WKY15W, n =6;WKY30W, n =6). The control group were treated with tap water. Losartan or captopril was dissolved in tap water and given to SHRLos or SHRCap at the dose of 30 mg·kg -1 ·d -1 or 100 mg·kg -1 ·d -1 . The rats were sacrificed after 15 weeks and free wall and septum of left ventricular were examined. Results (1) Angiotension Ⅱ, aldosterone, hydroxyproline, ratio of of typeⅠ/Ⅲ collagens in myocardium of SHR were increaed significantly than age matched WKY( P 0 01) Collagen α/β ratio and metalloproteinase 1 activity were decreased. (2) After treatment with losartan or captopril, angiotension Ⅱ, aldosterone, ratio Ⅰ/Ⅲ collagens in myocardium of SHR were decreased substantially. The ratio of collagen α/β and metalloproteinase 1 activity were increased in treatment groups. Losartan or captopril reverse myocardial fibrosis. (3) Losartan is more effective than captopril in the improve collagen phenotypes, decreases in cross linked and promote metalloproteinase 1 activity ( P 0 01). Conclusion Losartan and captopril reverse myocardial fibrosis not only by decreasing collagen content and cross linked but also improvement collagen of phenotypes and promoted metalloproteinase 1 activity.