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At least 991 records · Page 55Linked to original sources
PubMed1994

Fibrosis and myocardial ACE: possible substrate and independence from circulating angiotensin II.

In order to determine the relation between myocardial fibrosis and (1) angiotensin converting enzyme (ACE) binding density, (2) receptor binding of ACE-related peptides, angiotensin II (AngII) and bradykinin (BK), and (3) the regulation of myocardial ACE by circulating Ang II, we used in vitro quantitative autoradiography to localize and assess ACE ([125I]351A), AngII receptor (125I[Sar1, IIe8]AngII), and BK receptor ([125I]Tyr8) binding densities in the rat myocardium. The experimental groups were (1) AngII (9 micrograms/h subcutaneously) or aldosterone (0.75 microgram/h subcutaneously in uninephrectomized rats on a high-sodium diet) administered by implanted minipump to chronically increase or decrease circulating AngII, respectively, (2) unoperated, untreated age- and sex-matched control rats, and (3) age- and sex-matched uninephrectomized control rats on a high-sodium diet. In the same heart studied at 2, 4, and 6 weeks of hormone treatment, serial sections were assessed for myocardial (hematoxylin and eosin) and fibrillar collagen (picrosirius red) morphology. The authors found that (1) marked ACE binding was coincident with sites of fibrous tissue that appeared in both ventricles as either a perivascular fibrosis of intramyocardial coronary arterioles or microscopic scarring in response to AngII or aldosterone infusion, (2) ACE binding was independent of circulating AngII, (3) BK, not AngII, receptor binding density was markedly increased at fibrous tissue sites, and (4) high-density ACE and BK receptor binding were anatomically coincident. Thus, in these experimental models, ACE is related to fibrous tissue formation where it may use BK, not angiotensin I, as a substrate, and its binding density is independent of circulating AngII.

Aldosterone↗
PubMed1997

Chymase is activated in the hamster heart following ventricular fibrosis during the chronic stage of hypertension.

Chronic pressure overload induces cardiac tissue remodeling. Chymase is known to regulate matrix metabolism and angiotensin II formation. In the present study, we investigated the pathophysiological functions of chymase in the pressure-overloaded hamster heart induced by a two-kidney, one-clip (2K1C) hypertension procedure. Fibrosis and apoptosis were observed in the pressure-overloaded hearts of 2K1C hamsters 32 weeks after clipping, but these histological changes were not detected at 16 weeks. Heart chymase-like activity of 2K1C hamsters at 32 weeks increased 5.2-fold compared with that at 16 weeks, while angiotensin-converting enzyme was not activated. Chymase might be involved in cardiac tissue remodeling during the chronic stage of hypertension.

Animals↗
PubMed2006

Enhancement of cardiac oxidative stress by tachycardia and its critical role in cardiac hypertrophy and fibrosis.

OBJECTIVE: To examine the mechanism and significance of tachycardia-induced cardiac damage, using azelnidipine, a relatively new dihydropyridine calcium channel blocker which does not increase heart rate. METHODS: Comparing azelnidipine and amlodipine, we examined the cardiac effects and the direct effects on a sinus node/atrial preparation in stroke-prone spontaneously hypertensive rats (spSHRs). By pacing the right atrium, we examined the effect of tachycardia per se on cardiac oxidative stress. Using apocynin, a reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, we investigated the role of oxidative stress in cardiac remodelling. RESULTS: Azelnidipine suppressed cardiac hypertrophy, fibrosis, NADPH oxidase and superoxide in spSHRs more potently than amlodipine, and was associated with lower heart rates than amlodipine. Azelnidipine caused a greater reduction than amlodipine in the beat rate of the sinus node/atrial preparation of spSHRs. A 10 or 20% increase in heart rate, independent of blood pressure or sympathetic nerve activity, significantly enhanced cardiac NADPH oxidase activity, superoxide and activated mitogen-activated protein kinases. Reduction of cardiac oxidative stress by apocynin led to the suppression of cardiac hypertrophy, inflammation and fibrosis in spSHRs, beyond its hypotensive effect. CONCLUSIONS: Our work provided evidence that the increase in heart rate per se, independent of sympathetic nerve activity, enhances cardiac oxidative stress and activates mitogen-activated protein kinases, which seem to be responsible for cardiac remodelling. Azelnidipine, without causing an increase in heart rate, has the potential to be useful for the treatment of cardiac remodelling.

Amlodipine↗
PubMed1993

Comparison of morphologic findings in spontaneously occurring hypertrophic cardiomyopathy in humans, cats and dogs.

Morphologic features of spontaneously occurring hypertrophic cardiomyopathy (HC) were compared in 38 humans, 51 cats and 10 dogs. Asymmetric hypertrophy of the ventricular septum, marked disorganization of cardiac muscle cells, abnormal intramural coronary arteries and myocardial fibrosis were each present in the ventricular septum of human, feline, and canine forms of HC; these abnormalities were generally more severe and most frequently identified in humans. Asymmetric left ventricular hypertrophy (based on the calculated septal-to-free wall thickness ratio) was most common in humans (31 of 38 [81%]) and dogs (8 of 10 [80%]), as compared with cats (16 of 51 [31%]; p < 0.001) with HC; in all 3 species, hypertrophy was often diffuse, involving substantial portions of the anterolateral and posterior free walls, and the ventricular septum. Marked septal disorganization (> or = 5% of the tissue section) was present in 35 patients (92%), but in only 14 cats (27%) and 2 dogs (20%) (p < 0.001). Abnormal intramural coronary arteries occurred with similar frequency in the ventricular septum of patients (n = 25; 66%), cats (n = 38; 74%) and dogs (n = 6; 60%) (p < NS). Moderate-to-severe septal fibrosis was identified more commonly in humans (15 of 38 [39%]) than in animals (13 of 61 [21%]; p < 0.001). In all 3 species, abnormal intramural coronary arteries were most commonly observed within or at the margins of areas of fibrous tissue. These morphologic findings describe spontaneously occurring models of HC in cats and dogs with substantial structural similarities to the well-recognized disease entity in humans.

Adolescent↗
PubMed1994

Myocyte cellular hypertrophy is responsible for ventricular remodelling in the hypertrophied heart of middle aged individuals in the absence of cardiac failure.

OBJECTIVE: The aim was to measure changes in the numbers and size of ventricular myocytes in human hearts with marked ventricular hypertrophy and no clear signs of cardiac failure, to determine whether myocyte cellular hypertrophy is the only factor involved in the increase in cardiac mass. METHODS: Morphometric techniques were applied to estimate the number of myocyte nuclei per unit volume of myocardium which, in combination with the determination of the volume percent of myocytes, allowed the computation of the average myocyte cell volume per nucleus and total number of myocyte nuclei in the ventricles. Subsequently, the volume fraction of replacement fibrosis in the tissue was assessed and absolute component volumes in the ventricles obtained. RESULTS: Eight hypertrophied human hearts, weight 561(SD 68) g, were collected at necropsy from hypertensive patients who died from non-cardiac causes and were compared with eight normal hearts, weight 387(37) g, obtained from healthy individuals who also died from non-cardiac causes. With cardiac hypertrophy, left and right ventricular weight increased by 53% and 57%, whereas myocyte cell volume increased by 112% and 84%, respectively. The disproportion between the increase in ventricular weight and the increase in myocyte volume was due to a 30% and 16% loss in left and right ventricular myocytes following hypertensive hypertrophy. Myocyte loss also provoked a 319% and a 188% increase in the amount of replacement fibrosis in the left and right ventricular myocardium. These tissue and cellular processes resulted in an expansion in ventricular mass which exceeded the thickening of the wall so that an increase in cavitary volume occurred in both ventricles. CONCLUSIONS: Myocyte cellular hypertrophy is responsible for ventricular hypertrophy in hypertensive cardiomyopathy in its compensated stage. Myocyte loss precedes the impairment in ventricular pump function and may be implicated in the initiation of ventricular maladaptation.

Cardiomegaly↗
PubMed1995

Does ACE inhibition limit structural changes in the heart following myocardial infarction?

A recent series of experiments in our laboratory were designed to elucidate the cellular changes that underlie the cardiac remodelling response following myocardial infarction (MI) in the rat as well as the potential role of the renin-angiotensin system (RAS) in this response. Inhibition of the RAS interferes with cardiomyocyte hypertrophy, interstitial cell DNA synthesis, and collagen deposition; these effects are mediated through the angiotensin II AT1 receptor subtype. Also, vascular outgrowth is functionally diminished, an effect that seems to depend on AT2 receptor activation. The intracardiac RAS may be involved in the wound healing response in the infarct area. However, we found no evidence for activation of the RAS in the remnant myocardium, which suggests that myocyte hypertrophy and interstitial fibrosis depend on activation of the systemic RAS. During the first weeks following MI, therapy of choice should thus inhibit the systemic RAS while allowing the wound-healing response of the intracardiac RAS, i.e. selective AT1 antagonists are appropriate early after MI. AT2 antagonists administered at that time can inhibit the cardiac vascularization response and cause a further decrease in level of cardiac function.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

The cellular basis of dilated cardiomyopathy in humans.

The present investigation was designed to evaluate whether end-stage cardiac failure in patients affected by dilated cardiomyopathy (DC) was dependent upon extensive myocyte cell death with reduction in muscle mass or was the consequence of collagen accumulation in the myocardium independently from myocyte cell loss. In addition, the mechanisms of ventricular dilation were analysed in order to determine whether the changes in cardiac anatomy were important variables in the development of intractable congestive heart failure. DC is characterized by chamber dilation, myocardial scarring and myocyte hypertrophy in the absence of significant coronary atherosclerosis. However, the relative contribution of each of these factors to the remodeling of the ventricle is currently unknown. Moreover, no information is available concerning the potential etiology of collagen deposition in the myocardium and the changes in number and size of ventricular myocytes with this disease. Morphometric methodologies were applied to the analysis of 10 DC hearts obtained from patients undergoing cardiac transplantation. An identical number of control hearts was collected from individuals who died from causes other than cardiovascular diseases. DC produced a 2.2-fold and 4.2-fold increase in left ventricular weight and chamber volume resulting in a 48% reduction in mass-to-volume ratio. In the right ventricle, tissue weight and chamber size were both nearly doubled. Left ventricular dilation was the result of a 59% lengthening of myocytes and a 20% increase in the transverse circumference due to slippage of myocytes within the wall. Myocardial scarring represented by segmental, replacement and interstitial fibrosis occupied approximately 20% of each ventricle, and was indicative of extensive myocyte cell loss. However, myocyte number was not reduced and average cell volume increased 2-fold in both ventricles. In conclusion, reactive growth processes in myocytes and architectural rearrangement of the muscle compartment of the myocardium appear to be the major determinants of ventricular remodeling and the occurrence of cardiac failure in DC.

Autopsy↗
PubMed1999

Beta-adrenergic receptor blockade arrests myocyte damage and preserves cardiac function in the transgenic G(salpha) mouse.

Transgenic (TG) mice with cardiac G(salpha) overexpression exhibit enhanced inotropic and chronotropic responses to sympathetic stimulation, but develop cardiomyopathy with age. We tested the hypothesis that cardiomyopathy in TG mice with G(salpha) overexpression could be averted with chronic beta-adrenergic receptor (beta-AR) blockade. TG mice and age-matched wild-type littermates were treated with the beta-AR blocker propranolol for 6-7 months, starting at a time when the cardiomyopathy was developing but was not yet severe enough to induce significant cardiac depression (9.5 months of age), and ending at a time when cardiac depression and cardiomyopathy would have been clearly manifest (16 months of age). Propranolol treatment, which can induce cardiac depression in the normal heart, actually prevented cardiac dilation and the depressed left ventricular function characteristic of older TG mice, and abolished premature mortality. Propranolol also prevented the increase in myocyte cross-sectional area and myocardial fibrosis. Myocyte apoptosis, already apparent in 9-month-old TG mice, was actually eliminated by chronic propranolol. This study indicates that chronic sympathetic stimulation over an extended period is deleterious and results in cardiomyopathy. Conversely, beta-AR blockade is salutary in this situation and can prevent the development of cardiomyopathy.

Adenylyl Cyclases↗
PubMed1997

Local angiotensin II and myocardial fibrosis.

Tissue repair appears in the infarcted heart at both infarcted and noninfarcted myocardium. Experimental evidence gathered to date indicates that myoFb are the predominant cell responsible for collagen formation at sites of repair in the rat heart and related structures. These phenotypically transformed fibroblast-like cells are not normal residents of ventricular tissue. They appear on day 4 at sites of injury and remain abundant for weeks therefore. MyoFb express type I collagen mRNA and ACE and AT1 receptors. ACE inhibitors or AT1 receptor antagonists attenuate collagen accumulation in both infarcted and noninfarcted myocardium. These findings suggest locally generated AngII may have an autocrine function in regulating myoFb collagen turnover.

Angiotensin II↗
PubMed1995

Significance of detection of enterovirus RNA in myocardial tissues by reverse transcription-polymerase chain reaction.

Enteroviruses are known to have association with human myocarditis and dilated cardiomyopathy (DCM). We screened biopsy specimens from patients with active myocarditis or DCM, and myocardial tissues from autopsy cases without cardiac diseases using polymerase chain reaction (PCR) gene amplification. Positive enteroviral signals were demonstrated from 4 of 5 patients with active myocarditis (80%), 7 of 42 patients with DCM(17%) and 3 of 27 autopsies (11%). Out of 7 PCR positive patients with DCM, 3 cases showed hypertrophy and disarray of cardiocytes, fibrosis in the interstitium, and a few inflammatory infiltrates. The remaining 4 cases with DCM and 3 PCR positive autopsy cases did riot exhibit histological findings compatible with those in myocarditis. Our results support the observations that enteroviruses are common aetiologic agents of myocarditis, and some cases of DCM. Our results also suggest the possibility that in some cases enteroviruses may persist in the myocardium without causing apparent pathological changes.

Adult↗
PubMed1997

Sudden and unexpected death in clinically 'silent' Chagas' disease. A hypothesis.

BACKGROUND: Chagas' heart disease presents an interesting model of cardiac autonomic nerve dysfunction associated with morphologic lesions. A lack of quantitative evaluation of the latter suggested this study in which hearts from 34 subjects who were serum-positive for Chagas' disease but had no clinical evidence of it and who died suddenly and unexpectedly, out-of-hospital, were examined. METHODS AND RESULTS: By systematic myocardial sampling the histologic area was measured to establish: (a) the number of focal lymphocytic infiltrates x 100 mm2 and average number of lymphocytes per focus; (b) number of foci of, and myocells with, coagulative myocytolysis (contraction band necrosis) x 100 mm2; and (c) the percentage of substitutive myocardial fibrosis. In all cases findings were: (a) intermyocellular lymphocytic infiltrates (6 +/- 6 foci x 100 mm2); (b) coagulative myocytolysis (3 +/- 5 foci and 26 +/- 56 myocells x 100 mm2). CONCLUSIONS: In all 34 subjects quantitative analysis showed extensive lymphocytic infiltrates and myocardial damage typical of catecholamine cardiotoxicity. These two acute or active histological changes may explain their sudden demise produced by focal denervation with regional asynergy and consequent compensatory adrenergic stimulus with myotoxicity and malignant arrhythmia.

Acquired Immunodeficiency Syndrome↗
PubMed1996

[Complicated course of rheumatoid arthritis with pulmonary involvement, myocardial fibrosis and sleep apnea syndrome].

We report on a 67 year old man in whom the chest x-ray revealed marked interstitial opacities in both lungs. The diagnosis of Rheumatoid Arthritis (RA) was established by the presence of five criteria of the American College of Rheumatology for diagnosing RA. High resolution computertomography of the chest confirmed the abnormalities seen in the conventional chest x-ray. A biopsy, taken by open lung surgery, showed the typical pattern of pulmonary involvement in RA and confirmed the association of RA and interstitial lung fibrosis. The histologic examination pointed out lymphocytic infiltration of the bronchies, thickened alveolar walls with lymphoplasmarcellular infiltration and an increase in fibrous connective tissue. A congestive heart failure with severe arrhythmias and an obstructive sleep apnea syndrome (OSAS) were diagnosed in addition. The rhythm disturbances were attributed to the participation of the myocardium in RA and/or by the OSAS. By the treatment with prednisolone, methotrexate, mexiletine and continuous positive airway pressure (CPAP) the rhythm disturbances were alleviated and the patient's condition improved.

Aged↗
PubMed2003

An unusual case of recurrent Loffler endomyocarditis of the aortic valve.

Idiopathic hypereosinophilic syndrome is a rare systemic disease with an unexplained elevated eosinophil count. Loffler endomyocarditis is hypereosinophilic syndrome with endocardial fibrosis and restrictive cardiomyopathy. The atrioventricular valves are frequently involved, causing valvular regurgitation. Previously, there has been one case report of combined aortic and mitral valve involvement with Loffler endomyocarditis that was treated with bivalvular replacement. We describe a previously healthy 50-year-old man diagnosed with Loffler endomyocarditis complicated by peripheral thromboembolism and severe aortic regurgitation due to valve fibrosis and fibrotic vegetation on the aortic valve. He underwent embolectomy and aortic valve replacement in addition to treatment for his hypereosinophilia. He later presented with cardiomyopathy with severe aortic insufficiency due to the destruction of the aortic valve prosthesis by sterile fibrinous vegetation. To our knowledge, this is the second case in the literature in which Loffler endomyocarditis involves the aortic valve and the first patient in whom only the aortic valve is involved.

Aortic Valve↗
PubMed1997

Fibrosis of atria and great vessels in response to angiotensin II or aldosterone infusion.

OBJECTIVE: Myocardial fibrosis, associated with increased expression of angiotensin converting enzyme (ACE) and bradykinin (BK) receptor binding at sites of tissue repair, accompanies chronic elevations in circulating angiotensin II (AngII) and/or aldosterone (ALDO) that simulate chronic cardiac failure. A role for increased ventricular wall stress, associated with arterial hypertension, that can accompany such neurohormonal activation when ventricular function is not compromised, has been held responsible for this structural remodeling. To address this proposition, we monitored morphology of right and left atria and pulmonary artery, where stress is not increased, and compared these structures with hypertensive aorta. METHODS: Experimental groups included: (1) unoperated and untreated controls; (2) intact rats receiving AngII (9 micrograms/h) for 2 weeks and which causes arterial hypertension; (3) uninephrectomized control rats on a high sodium diet for 6 weeks; and (4) uninephrectomized rats receiving ALDO (0.75 micrograms/h) and a high sodium diet for 6 weeks and which results in gradual onset arterial hypertension. Fibrosis was identified by light microscopy in sections stained with collagen specific picrosirius red, while ACE, AngII and BK receptors binding were localized and quantitated by in vitro autoradiography using 125I-351A, 125I[Sar1,Ile8]AngII, and 125I[Tyr8]BK, respectively. AngII receptor subtype was defined by the presence of excess AT1 (losartan) or AT2 (PD123177) receptor antagonists, respectively. RESULTS: With either AngII or ALDO administration, and compared to controls, we found: (1) microscopic scarring that replaced lost myocytes in both left and right atria; (2) an increase in adventitial collagen of both pulmonary artery and aorta (perivascular fibrosis); (3) markedly increased ACE binding at fibrous tissue sites in both atria and great vessels; (4) unchanged atrial and great vessel AT1 receptor binding; and (5) significantly increased BK receptor binding at sites of atrial and perivascular fibrosis. CONCLUSIONS: Thus, the appearance of atrial fibrosis and perivascular fibrosis of aorta and pulmonary artery, together with associated increase in ACE and BK receptor binding, in rats receiving AngII or ALDO suggests these responses are not related to altered ventricular wall stress or arterial hypertension, but rather to these effector hormones of the circulating renin-angiotensin-aldosterone system. Local BK, regulated by ACE found in fibrous tissue and BK receptor binding may play a role in structural remodeling of atria and great vessels in these rat models that stimulate chronic cardiac failure.

Aldosterone↗
PubMed2006

Inhibition of urokinase-type plasminogen activator or matrix metalloproteinases prevents cardiac injury and dysfunction during viral myocarditis.

BACKGROUND: Acute viral myocarditis is an important cause of cardiac failure in young adults for which there is no effective treatment apart from general heart failure therapy. The present study tested the hypothesis that increased expression of the proteinases urokinase-type plasminogen activator (uPA) and matrix metalloproteinases (MMPs) is implicated in cardiac inflammation, injury, and subsequent failure during Coxsackievirus-B3 (CVB3)-induced myocarditis. METHODS AND RESULTS: First, we showed increased expression and activity of uPA and MMP-9 in wild-type mice at 7 days of CVB3-induced myocarditis. Targeted deletion of uPA, which resulted in reduced MMP activity and cytokine expression or inhibition of MMPs by adenoviral gene overexpression of tissue inhibitor of metalloproteinases-1, decreased cardiac inflammation and reduced myocardial necrosis at 7 days and decreased cardiac fibrosis at 35 days after CVB3 infection. Importantly, loss of uPA or MMP activity prevented CVB3-induced cardiac dilatation and dysfunction, as determined by serial echocardiography. CONCLUSIONS: Loss of uPA or MMP activity reduces the cardiac inflammatory response after CVB3 infection, thereby protecting against cardiac injury, dilatation, and failure during CVB3-induced myocarditis.

Animals↗
PubMed2001

Brain natriuretic peptide appears to act locally as an antifibrotic factor in the heart.

In addition to cardiac myocyte hypertrophy, proliferation and increased extracellular matrix production of cardiac fibroblasts occur in response to cardiac overload. This remodeling of the cardiac interstitium is a major determinant of pathologic hypertrophy leading to ventricular dysfunction and heart failure. Atrial and brain natriuretic peptides (ANP and BNP) are cardiac hormones produced primarily by the atrium and ventricle, respectively. Plasma ANP and BNP concentrations are elevated in patients with hypertension, cardiac hypertrophy, and acute myocardial infarction, suggesting their pathophysiologic roles in these disorders. ANP and BNP exhibit diuretic, natriuretic, and vasodilatory activities via a guanylyl cyclase-coupled natriuretic peptide receptor subtype (guanylyl cyclase-A or GC-A). Here we report the generation of mice with targeted disruption of BNP (BNP-/- mice). We observed focal fibrotic lesions in ventricles from BNP-/- mice with a remarkable increase in ventricular mRNA expression of ANP, angiotensin converting enzyme (ACE), transforming growth factor (TGF)-beta3, and pro-alpha1(I) collagen [Col alpha1(I)], which are implicated in the generation and progression of ventricular fibrosis. Electron microscopic examination revealed supercontraction of sarcomeres and disorganized myofibrils in some ventricular myocytes from BNP-/- mice. No signs of cardiac hypertrophy and systemic hypertension were noted in BNP-/- mice. In response to acute cardiac pressure overload induced by aortic constriction, massive fibrotic lesions were found in all the BNP-/- mice examined, accompanied by further increase of mRNA expression of TGF-beta3 and Col alpha1(I). We postulate that BNP acts as a cardiocyte-derived antifibrotic factor in the ventricle.

Alleles↗
PubMed1983

[Myocardial infarction and myocardial ischemia in newborn children and infants, not secondary to an abnormal coronary].

Three cases (one, newborn infant and two infants--one of them recently published--) who present electrocardiographic and enzymatic alterations comparative with diagnosis of ischemia and myocardial infarction are reported. Rarity of this entity in infants is stressed as most of published cases are secondary to ananomolous coronary artery. Etiology of the cases presented shows a myocardiac fibrosis with Schwachman's syndrome in one case, a coronary thrombosis secondary to a disseminated intravascular coagulation in a second case, and finally a generalized hypoplasia of coronary arteries. Hypoxia appears in these cases a factor acting in favour of myocardial ischemia. Diagnostic criteria of acute myocardial infarction are based on typical electrocardiogram and rise of isoenzymes of LDH and CPK-MB. Although rare, it is a diagnosis to be considered in cases of unknow cardiac insufficiency in newborns and infants.

Coronary Disease↗
PubMed1995

Pharmacological modulation of cardiac fibroblast function.

The cardiac interstitium is composed of nonmyocyte cells and a structural protein network which plays a dominant role in governing the structure, architecture, and mechanical behavior of the myocardium. The heterogeneity in myocardial structure, created by the altered behavior of nonmyocyte cells, particularly cardiac fibroblasts which are responsible for myocardial collagen metabolism and fibrous tissue accumulation, may largely explain the appearance of diastolic and/or systolic myocardial failure. Regulatory mechanisms that are related to the fibrous tissue response in various cardiovascular diseases, e.g., hypertensive heart disease, dilated cardiomyopathy or post myocardial infarction, are of primary clinical interest. A better understanding of the hitherto neglected role of cardiac fibroblasts in mediating an adverse structural remodeling of the myocardium will lead to specific pharmacologic agents that interfere with the fibrous tissue response. Several lines of evidence based on in vivo and in vitro studies suggest that circulating and tissue renin-angiotensin-aldosterone systems (RAAS) are involved in the structural remodeling of the nonmyocyte compartment, including the cardioprotective effects of angiotensin converting enzyme (ACE) inhibition or aldosterone receptor antagonism that was found to prevent myocardial fibrosis in the rat with renovascular or genetic hypertension. In cultured adult cardiac fibroblasts, an angiotensin (Ang)II- or aldosterone-mediated dose-dependent increase in collagen synthesis could be completely abolished by the use of AngII type 1 or mineralocorticoid receptor antagonists, respectively. Likewise, the AngII-mediated decrease in the activity of matrix metalloproteinase 1, the key enzyme for interstitial collagen degradation, could be antagonized by AngII receptor blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗