Effects of telmisartan and amlodipine on myocardial fibrosis and serum levels of angiotensin-(1-7) in hypertensive rats with abdominal aortic constriction

AIM: To evaluate the preventive effects of telmisartan (TMST) and amlodipine (ALDP) on myocardial fibrosis in hypertensive rats with abdominal aortic constriction (AAC) and to observe the changes of angiotensin-(1-7) ［Ang-(1-7)］ levels. METHODS: AAC (n=24) and sham operation (n=8) were performed on 8-week-old male Sprague Dawley rats. After 1 week of operation, AAC rats were randomly divided into three groups: TMST (n=8), ALDP (n=8) and AAC control (n=8), respectively. The first two groups were treated by TLST and ALDP at doses of 5 mg/(kg·day), respectively. After 8 weeks, serum levels of Ang-(1-7) were determined by ELISA and myocardial collagen volume fraction (CVF), collagen type I, type III and I/III were assessed by sirius red staining combined with computer image analysis. RESULTS: Compared with those in sham group, the myocardial CVF, integral optical density (IOD) values of collagen type I and I/III increased in TLST group, ALDP group and AAC control group (P<0.05), with the parameters in treatment groups significantly lower than those in AAC control group, and the parameters in TMST group significantly lower than those in ALDP group. IOD values of collagen type III also were on the rise, with the values in treatment groups significantly lower than those in AAC control group, but there were no significant difference between TMST group and ALDP group. Compared with AAC control group, TMST and ALDP both increased serum levels of Ang-(1-7), but only the increase in TMST group was significant (P<0.05). However, no significant difference was observed between the two groups. Relationships between serum levels of Ang-(1-7) and myocardial CVF, IOD values of collagen type I and type III, I/III were negatively correlated (P<0.05), and r value was -0.47 (P<0.05), -0.38 (P<0.05), -0.32 (P<0.05）and -0.41 (P<0.05), respectively. CONCLUSION: Both TMST and ALDP prevent myocardial fibrosis in hypertensive rats with AAC but TMST seems to be more effective. Ang-(1-7) may be involved in the process of inhibiting myocardial fibrosis with TMST.