Aldosterone Blockade Reduces Mortality without Changing Cardiac Remodeling in Spontaneously Hypertensive Rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Myocardial remodeling and dysfunction are induced by chronic food restriction in spontaneously hypertensive rats

Several studies have shown alterations in hearts from animals subjected to food restriction (FR). However, few experiments in hearts evaluating pressure overload have been reported. We examined the effects of chronic FR on myocardial function and morphology in spontaneously hypertensive rats (SHR). Sixty-day-old SHR were fed a control (C) or a restricted diet (daily intake reduced to 50% of amount of food consumed by the control group) for 90 days. Myocardial performance was studied in isolated left ventricular (LV) papillary muscle. Food restriction decreased body weight and LV weight; LV weight/body-weight ratio was lower in the food-restricted group (SHR-C, 2.84 +/- 0.21 mg/g; SHR-FR, 2.56 +/- 0.24 mg/g; P <.05). Food restriction did not change arterial systolic blood pressure. Myocyte surface area was lower in the food-restricted group (P <.01). Food restriction induced myocardial ultrastructural alterations including reduced sarcoplasm content, reduced and disorganized myofilaments, disorganized Z line, dilated sarcoplasmic reticulum, and deep infoldings of plasma membrane. Myocardial hydroxyproline concentration was increased in the restricted rats. Peak developed tension (P <.05) and maximum rate of tension development (P <.01) were decreased in the SHR-FR group. In conclusion, myocardium of SHR subjected to chronic FR presents attenuation of hypertrophy development, ultrastructural changes, increased collagen content, and systolic dysfunction. (c) 2006 Elsevier B.V. All rights reserved.

Myocardial fibrosis rather than hypertrophy induces diastolic dysfunction in renovascular hypertensive rats

The aim of the present study was to evaluate the-effect of interstitial fibrosis alone or associated with hypertrophy. on diastolic myocardial function in renovascular hypertensive rats. Myocardial function was evaluated in isolated papillary muscle from renovascular hypertensive Wistar rats (RHT, n = 14), renovascular hypertensive rats treated with the angiotensin converting enzyme inhibitor (ACEI) ramipril, 20 mg.kg(-1).day(-1) (RHT RAM, n = 14), and age-matched unoperated and untreated Wistar rats (CONT, n = 12). The ACEI treatment for 3 weeks allowed the regression of myocyte mass and the maintenance of interstitial fibrosis. Myocardial passive stiffness was analyzed by the resting tension - length relationship. The myocardial fibrosis was evaluated by measuring myocardial hydroxyproline (Hyp) concentration and by histological studies of the myocardium stained with hematoxylin and eosin or picrosirius red. Left ventricular weight was significantly higher in RHT (0.97 +/- 0.12 g) compared with CONT (0.66 +/- 0.06 g) and RHT RAM (0.69 +/- 0.14 g). The Hyp levels were 2.9 +/- 0.4, 3.4 +/- 0.3, and 3.8 +/- 0.4 mu g/mg of dry tissue for the CONT, RHT, and RHT RAM, respectively. Perivascular and interstitial fibrosis were observed in RHT and RHT RAM groups. There were lymphomononuclear inflammatory exudate and edema around arteries, involving adjacent myocytes in the RHT group. There was an increased passive stiffness in RHT and RHT RAM groups compared with the CONT group. In conclusion, our results indicate that the Impaired diastolic function in the renovascular hypertensive rats is related to interstitial fibrosis rather than to myocardial hypertrophy.

Direct effects of colchicine on myocardial function - Studies in hypertrophied and failing spontaneously hypertensive rats

The aging spontaneously hypertensive rat (SHR) is a model in which the transition from chronic stable left ventricular hypertrophy to overt heart failure can be observed. Although the mechanisms for impaired function in hypertrophied and failing cardiac muscle from the SHR have been studied, none accounts fully for the myocardial contractile abnormalities. The cardiac cytoskeleton has been implicated as a possible cause for myocardial dysfunction. If an increase in microtubules contributes to dysfunction, then myocardial microtubule disruption by colchicine should promote an improvement in cardiac performance. We studied the active and passive properties of isolated left ventricular papillary muscles from 18- to 24-month-old SHR with evidence of heart failure (SHR-F, n=6), age-matched SHR without heart failure (SHR-NF, n=6), and age-matched normotensive Wistar-Kyoto rats (WKY, n=5). Mechanical parameters were analyzed before and up to 90 minutes after the addition of colchicine (10(-5), 10(-4), and 10(-3) mol/L). In the baseline state, active tension (AT) developed by papillary muscles from the WKY group was greater than for SHR-NF and SHR-F groups (WKY 5.69+/-1.47 g/mm(2) [mean+/-SD], SHR-NF 3.41+/-1.05, SHR-F 2.87+/-0.26; SHR-NF and SHR-F P<0.05 versus WKY rats). The passive stiffness was greater in SHR-F than in the WKY and SHR-NF groups (central segment exponential stiffness constant, K-cs: SHR-F 70+/-25, SHR-NF 44+/-17, WKY 41+/-13 [mean+/-SD]; SHR-F P<0.05 versus; SHR-NF and WKY rats). AT did not improve after 10, 20, and 30 minutes of exposure to colchicine (10(-5), 10(-4), and 10(-3) mol/L) in any group. In the SHR-F group, AT and passive stiffness did not change after 30 to 90 minutes of colchicine exposure (10(-4) mol/L). In summary, the data in this study fail to demonstrate improvement of intrinsic muscle function in SHR with heart failure after colchicine. Thus, in the SHR there is no evidence that colchicine-induced cardiac microtubular depolymerization affects the active or passive properties of hypertrophied or failing left ventricular myocardium.

Effects of hypertension on maternal adaptations to pregnancy: experimental study on spontaneously hypertensive rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Food restriction induces in vivo ventricular dysfunction in spontaneously hypertensive rats without impairment of in vitro myocardial contractility

Cardiac structures, function, and myocardial contractility are affected by food restriction (FR). There are few experiments associating undernutrition with hypertension. The aim of the present study was to analyze the effects of FR on the cardiac response to hypertension in a genetic model of hypertension, the spontaneously hypertensive rat (SHR). Five-month-old SHR were fed a control or a calorie-restricted diet for 90 days. Global left ventricle (LV) systolic function was evaluated in vivo by transthoracic echocardiogram and myocardial contractility and diastolic function were assessed in vitro in an isovolumetrically beating isolated heart (Langendorff preparation). FR reduced LV systolic function (control (mean ± SD): 58.9 ± 8.2; FR: 50.8 ± 4.8%, N = 14, P < 0.05). Myocardial contractility was preserved when assessed by the +dP/dt (control: 3493 ± 379; FR: 3555 ± 211 mmHg/s, P > 0.05), and developed pressure (in vitro) at diastolic pressure of zero (control: 152 ± 16; FR: 149 ± 15 mmHg, N = 9, P > 0.05) and 25 mmHg (control: 155 ± 9; FR: 150 ± 10 mmHg, N = 9, P > 0.05). FR also induced eccentric ventricular remodeling, and reduced myocardial elasticity (control: 10.9 ± 1.6; FR: 9.2 ± 0.9%, N = 9, P < 0.05) and LV compliance (control: 82.6 ± 16.5; FR: 68.2 ± 9.1%, N = 9, P < 0.05). We conclude that FR causes systolic ventricular dysfunction without in vitro change in myocardial contractility and diastolic dysfunction probably due to a reduction in myocardial elasticity.

Alveolar bone healing process in spontaneously hypertensive rats (SHR). A radiographic densitometry study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hypotensive and vasorelaxing effects of the new NO-donor [Ru(terpy)(bdq)NO+](3+) in spontaneously hypertensive rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)