| ObjectiveMyocardial fibrosis not only is one of important mechanisms on the myocardial remodeling of hypertension ,coronary heart disease and heart failure, but also is an important feature of cardiac aging. Myocardial fibrosis with aging might be associated with rennin angiotensin system ( HAS) and changes of various fibrosis related polypeptides. The effective molecular of HAS is angiotensin II ( Ang II ). Some studies found that Ang II stimulated the release of transforming growth factor - 1 (TGF - 1) in the fibroblasts by AT1 receptor, activated the transcription of TGF - 1 and made TGF - 1 change from silent state into active state. It had been identified that TGF - 1 could cause fibrosis in hypertension, myocardial infarction etc, but reports on its effect on myocardial fibrosis in the old rats are few and disputed. Losartan is competitive to Ang II in binding with AT1 receptor, Losartan could inhibit the development of myocardial fibrosis in rats with spontaneous hypertension, but the report whether Losartan could inhibit the development of myocardial fibrosis in the old rats was few.This experiment discussed mechanism of myocardial fibrosis in old rats by studying changes of cardiac structure and TGF - 1 in rats with aging, and observed change of myocardial interstitial in old rats after given Losartan. It could provide a sound theoretical basis for preventing and reversing myocardial fibrosis with aging and recovering heart normal structure and clinical medication.Methods1. AnimalsThirty Wistar rats were divided into three groups: 10 young rats (3 monthsold) ; 20 old rats (18 months old) were randomly divided into 2 groups, 10 rats were in the old group, 10 rats were given Losartan (20mg/kg/d in 2 ~3ml distilled water) for 8 weeks. In the young and the old group, rats were given the same dose distilled water for 8 weeks. One rat died in the Losartan group.2. Isolated heart preparationWeighing rats, abdominal anesthesia by 3% sodium pentobarbital (30mg/ kg) , opening chests, taking hearts out, weighing left ventricle (LVW) and calculating left ventricular mass index ( LVMI).3. Detection of hydroxyproline concentration ( HC)The content of hydroxyproline in the collagen is fixed, so it can show the extent of myocardial fibrosis. After myocardial tissue were digested and hydro-lyzed, absorbencies (OB) of the solution were detected with spectrophotometer (550nm). HC ( |xg/100mg) = [ ( OB of myocardial tissues - OB of blank tube) -r (OB of standard tube - OB of blank tube) ] x concentration of standard tube.4. Van - Greson staining of myocardial collagenThe hearts were generally fixed ,embedded and made into the sections. The sections were stained with 1% acid fuchsin and 0. 5% saturated picric acid (Van - Greson staining, VG staining). Collagen Volume Fraction (CVF) and perivascular Circumferential Area ( PVCA) were examined with computer -based video analysis system and analysis software package. CVF = the area of collagen/the total area, the area of collagen didnt include the area of perivascular collagen; PVCA = the area of collagen around the small artery/ the area of the small arterial antrum.5. Immunohistochemical staining of TGF - 1 Immunohistochemical staining of TGF - 1 were performed with the methodof SP. The expressions of TGF - 1 were quantified with computer - based video analysis system and analysis software package. The judging standard: 0: no expression; 1: a vitally small quantity of expression, the positive area <25% ; 2; a small quantity of expression, the positive area < 50% ; 3: a medium quantity of expression, the positive area <75% ; 4: abundant expression, the positive area > 75%.6. Statistical analysisAll data were expressed as mean å¤ standard deviation. Statistical comparisons were made by t - test, and the relativity was made by rank correlation analysis. All the statistical analyses were done with statistical software (SPSS11. 0). Statistical significance was defined at P <0. 05.Results1. Comparisons of BW\ LVW a... |
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