Effects of Losartan on Cardiomyocyte Proliferation and Perivascular Collagen of Myocardium in Spontaneously Hypertensive Rats

To explore the effects of anti-hypertensive therapy with angiotensin Ⅱ AT 1 receptor antagonist- losartan on the proliferation of left ventricular cardiomyocyte and perimyocardial collagen fibers in spontaneously hypertensive rats (SHR).Sixty-three 12-week-old male SHRs were divided into 3 groups : ①Treated group (SHR-L), losartan (30 mg·kg -1·d -1) was administered in 21 SHRs for 4 ～12 wks ;②Untreated group (SHR-C), losartan was not given in 21 SHRs; and ③ Normal control group ,21 WKY rats were included.. Hypotensive therapy was scheduled in the treated group for 12 wks. The systolic blood pressure and left ventricle weight (LVW) were measured in three groups for calculation of the ratio between LVW and body weight (LV/BW). In addition, myocardial interstitial collagen volume fraction (CVF) and myocardial perivascular collagen area (PVCA) were assayed. The hearts and aortas were stained with HE and Sirius dyes.①As compared with age-matched SHR-C, the LV/BW ratio in SHR-L markedly decreased (P0.01), becoming more prominent with the prolongation of therapeutic duration .②CVF and PVCA in 12～24 week-old WKY rats significantly increased(P0.05); while those in SHR-C rose with increasing week-age (P0.05). Significant difference existed between CVF/PVCA of SHR-C and those of age-matched WKY rats (P0.05). The CVF and PVCA in SHR-L group distinctly declined .in comparison with those in SHR-C group (P0.05), but they were close to those in WKY rats (P0.05).[Conclusion]Administration of losartan can obviously inhibit the abnormal proliferation of collagen in myocardium and promote its degradation. Therefore, losartan prevents and hinders myocardial fibrosis , thus reverses the left ventricle hypertrophy in SHR.