Enalapril and losartan reduced cardiac mass and improved coronary hemodynamics in SHR

Physical exercise is essential for increasing ventricular contractility in hypertensive rats treated with losartan

The treatment of hypertensive patients with losartan is very common. Despite the reduction in blood pressure, its effects on cardiac contractility and sympathetic autonomic drive are still controversial. In turn, aerobic physical training (APT) also presents an important therapeutic option, providing significant improvements in cardiovascular autonomic control, however little is known about its effects on cardiac contractility, especially when associated with losartan. Therefore, we investigated in spontaneously hypertensive rats (SHR) the effects of losartan and APT on cardiac hemodynamics and functionality, with emphasis on autonomic tonic balance and cardiac contractility. Sixty-four SHR (18 weeks old) were divided into four groups (N = 16): vehicle; vehicle submitted to APT through swimming for 12 weeks; treated with losartan (5 mg·kg-1·d-1) for 12 weeks; and treated with losartan associated with APT. The groups were submitted to cardiac morphological and functional analysis by echocardiography; double blockade of cardiac autonomic receptors with atropine and propranolol; and coronary bed reactivity and left ventricular contractility analyses by the Langendorff technique. APT improved functional parameters and autonomic balance by reducing sympathetic drive and/or increasing vagal drive. In contrast, it promoted a concentric remodeling of the left ventricle (LV). Treatment with losartan reduced sympathetic autonomic drive and cardiac morphological parameters, but there were no significant gains in cardiac functionality and contractility. When combined, the concentric remodeling of the LV to APT was abolished and gains in cardiac functionality and contractility were observed. Our findings suggest that the effects of losartan and APT are complementary and should be applied together in the treatment of hypertension. In spontaneously hypertensive rats, the combination of aerobic physical training with losartan treatment was crucial to greater blood pressure reductions and an increase in left ventricular contractility. Furthermore, losartan treatment prevented the concentric left ventricular remodeling caused by aerobic physical training.

Predictors of outcome after catheter ablation for atrial fibrillation: Group analysis categorized by age and type of atrial fibrillation

BACKGROUND

The outcome of catheter ablation could probably differ among patients with atrial fibrillation (AF), depending on age and AF type. We aimed to investigate the difference in predictors of outcome after catheter ablation for AF among the patient categories divided by age and AF type.

METHODS AND RESULTS

A total of 396 patients with AF (mean age 65.69 ± 11.05 years, 111 women [28.0%]) who underwent catheter ablation from January 2018 to December 2019 were retrospectively analyzed. We divided the patients into four categories: patients with paroxysmal AF (PAF) or persistent AF (PeAF) who were 75 years or younger (≤75 years) or older than 75 years (>75 years). Kaplan-Meier survival analysis demonstrated that patients with PAF aged ≤75 years had the lowest AF recurrence among the four groups (log-rank test, p = .0103). In the patients with PAF aged ≤75 years (N = 186, 46.7%), significant factors associated with recurrence were female sex (p = .008) and diabetes (p = .042). In the patients with PeAF aged ≤75 years (N = 142, 35.9%), the only significant factor associated with no recurrence was medication with a renin-angiotensin system inhibitor (p = .044). In the patients with PAF aged >75 years (N = 53, 14.4%), diabetes was significantly associated with AF recurrence (p = .021). No significant parameters were found in the patients with PeAF aged >75 years (N = 15, 4.1%).

CONCLUSIONS

Our findings indicate that the risk factors for AF recurrence after catheter ablation differed by age and AF type.

COVID-19: Understanding the impact of anti-hypertensive drugs and hydroxychloroquine on the ACE1 and ACE2 in lung and adipose tissue in SHR and WKY rats

Hypertensive individuals taking anti-hypertensive drugs from renin-angiotensin system inhibitors may exhibit a more severe evolution of the disease when contracting the SARS-CoV-2 virus (COVID-19 disease) due to potential increases in ACE2 expression. The study investigated ACE1 and ACE2 axes and hydroxychloroquine in the lungs and adipose tissue of male and female normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHRs). SHRs were treated with losartan (10 mg/kg/day) or captopril (10 mg/kg/day) for 14 days or 7 days with hydroxychloroquine (200 mg/kg/day) in drinking water. WKY rats were also treated for 7 days with hydroxychloroquine. Blood pressure (BP), protein, and mRNA expression of ACE1 and ACE2 were analyzed in serum, adipose, and lung tissues. Losartan and captopril reduced BP in both sexes in SHR, whereas hydroxychloroquine increased BP in WKY rats. Losartan reduced ACE2 in serum and lungs in both sexes and in adipose tissue of male SHRs. Captopril decreased ACE2 protein in the lung of females and in adipose tissue in both sexes of SHRs. Hydroxychloroquine decreased ACE1 and ACE2 proteins in the lungs in both sexes and adipose tissue in male SHRs. In female WKY rats, ACE2 protein was lower only in the lungs and adipose tissue. Losartan effectively inhibited ACE2 in male and captopril in female SHRs. Hydroxychloroquine inhibited ACE2 in male SHRs and female WKY rats. These results further our understanding of the ACE2 mechanism in patients under renin-angiotensin anti-hypertensive therapy and in many trials using hydroxychloroquine for COVID-19 treatment and potential sex differences in response to drug treatment.

Wave intensity analysis and its application to the coronary circulation

Wave intensity analysis (WIA) is a technique developed from the field of gas dynamics that is now being applied to assess cardiovascular physiology. It allows quantification of the forces acting to alter flow and pressure within a fluid system, and as such it is highly insightful in ascribing cause to dynamic blood pressure or velocity changes. When co-incident waves arrive at the same spatial location they exert either counteracting or summative effects on flow and pressure. WIA however allows waves of different origins to be measured uninfluenced by other simultaneously arriving waves. It therefore has found particular applicability within the coronary circulation where both proximal (aortic) and distal (myocardial) ends of the coronary artery can markedly influence blood flow. Using these concepts, a repeating pattern of 6 waves has been consistently identified within the coronary arteries, 3 originating proximally and 3 distally. Each has been associated with a particular part of the cardiac cycle. The most clinically relevant wave to date is the backward decompression wave, which causes the marked increase in coronary flow velocity observed at the start of the diastole. It has been proposed that this wave is generated by the elastic re-expansion of the intra-myocardial blood vessels that are compressed during systolic contraction. Particularly by quantifying this wave, WIA has been used to provide mechanistic and prognostic insight into a number of conditions including aortic stenosis, left ventricular hypertrophy, coronary artery disease and heart failure. It has proven itself to be highly sensitive and as such a number of novel research directions are encouraged where further insights would be beneficial.

An orally active angiotensin-(1-7) inclusion compound and exercise training produce similar cardiovascular effects in spontaneously hypertensive rats

Low angiotensin-(1-7) (Ang-(1-7)) concentration is observed in some cardiovascular diseases and exercise training seems to restore its concentration in the heart. Recently, a novel formulation of an orally active Ang-(1-7) included in hydroxy-propyl-beta-cyclodextrin (HPB-CD) was developed and chronically administered in experimental models of cardiovascular diseases. The present study examined whether chronic administration of HPB-CD/Ang-(1-7) produces beneficial cardiovascular effects in spontaneously hypertensive rats (SHR), as well as to compare the results obtained with those produced by exercise training. Male SHR (15-week old) were divided in control (tap water) or treated with HPB-CD/Ang-(1-7) (corresponding to 30μgkg(-1)day(-1) of Ang-(1-7)) by gavage, concomitantly or not to exercise training (treadmill, 10 weeks). After chronic treatment, hemodynamic, morphometric and molecular analysis in the heart were performed. Chronic HPB-CD/Ang-(1-7) decreased arterial blood pressure (BP) and heart rate in SHR. The inclusion compound significantly improved left ventricular (LV) end-diastolic pressure, restored the maximum and minimum derivatives (dP/dT) and decreased cardiac hypertrophy index in SHR. Chronic treatment improved autonomic control by attenuating sympathetic modulation on heart and vessels and the SAP variability, as well as increasing parasympathetic modulation and HR variability. Overall results were similar to those obtained with exercise training. These results show that chronic treatment with the HPB-CD/Ang-(1-7) inclusion compound produced beneficial effects in SHR resembling the ones produced by exercise training. This observation reinforces the potential cardiovascular therapeutic effect of this novel peptide formulation.

Matrix metalloproteinases cleave the beta2-adrenergic receptor in spontaneously hypertensive rats

We recently observed the enhanced serine and matrix metalloproteinase (MMP) activity in the spontaneously hypertensive rat (SHR) compared with its normotensive Wistar-Kyoto (WKY) rat and the cleavage of membrane receptors in the SHR by MMPs. We demonstrate in vivo that MMP-7 and MMP-9 injection leads to a vasoconstrictor response in microvessels of rats that is blocked by a specific MMP inhibitor (GM-6001, 1 microM). Multiple pathways may be responsible. Since the beta(2)-adrenergic receptor (beta(2)-AR) is susceptible to the action of endogenous MMPs, we hypothesize that MMPs in the plasma of SHRs are able to cleave the extracellular domain of the beta(2)-AR. SHR arterioles respond in an attenuated fashion to beta(2)-AR agonists and antagonists. Aorta and heart muscle of control Wistar rats were exposed for 24 h (37 degrees C) to fresh plasma of male Wistar and WKY rats and SHRs with and without doxycycline (30 microM) and EDTA (10 mM) to reduce MMP activity. The density of extracellular and intracellular domains of beta(2)-AR was determined by immunohistochemistry. The density of the extracellular domain of beta(2)-AR is reduced in aortic endothelial cells and cardiac microvessels of SHRs compared with that of WKY or Wistar rats. Treatment of the aorta and the heart of control Wistar rats with plasma from SHRs, but not from WKY rats, reduced the number of extracellular domains, but not intracellular domains, of beta(2)-AR in aortic endothelial cells and cardiac microvessels. MMP inhibitors (EDTA and doxycycline) prevented the cleavage of the extracellular domain. Thus MMPs may contribute to the reduced density of the extracellular domain of beta(2)-AR in blood vessels and to the increased arteriolar tone of SHRs compared with normotensive rats.

A New Hypothesis for Insulin Resistance in Hypertension Due to Receptor Cleavage

BACKGROUND: One of the most important unresolved issues in diabetes is the mechanism for the attenuated response to insulin, i.e. insulin resistance. AIMS AND METHODS: We hypothesize that the mechanism for the insulin resistance is due to uncontrolled protease activity in the plasma, on endothelial cells and in the tissue parenchyma. To examine this hypothesis we use of microzymographic techniques in the microcirculation, plasma zymography, and receptor labeling techniques with antibodies against an extracellular domain of the insulin receptor α. RESULTS: The spontaneously hypertensive rat has an enhanced proteolytic activity and significant cleavage of the receptor with attenuated glucose transport. We present evidence for insulin receptor cleavage in a high fat diet and a transgenic model of diabetes. CONCLUSION: These results suggest that cleavage of the extracellular domain of the insulin receptor, a situation that interferes with the ability for insulin to bind and provide an intracellular signal for glucose transport, may be involved in insulin resistance.

Localization of ACE2 in the renal vasculature: amplification by angiotensin II type 1 receptor blockade using telmisartan

Angiotensin-converting enzyme (ACE)2 is a carboxypeptidase that degrades angiotensin II and other peptides. In the kidney, ACE2 localization within the glomerulus and tubules is cell specific. This study was aimed to investigate the localization of ACE2 within the renal vasculature. We also studied the effect of the administration of a specific angiotensin II type 1 receptor blocker, telmisartan, on ACE2 expression in the renal vasculature. ACE2 and ACE were localized in renal arterioles using confocal microscopy and specific cell markers. Quantitative measurements of ACE2 and ACE mRNA were estimated in kidney arterioles isolated by laser capture microdissection using real-time PCR. In kidney arterioles, ACE was localized in the endothelial layer, whereas ACE2 was localized in the tunica media. In mice treated with telmisartan (2 mg.kg(-1).day(-1)) for 2 wk, ACE2 expression was increased by immunostaining, whereas ACE expression was decreased. This was reflected in a decrease in the ACE/ACE2 ratio compared with vehicle-treated controls (0.53 +/- 0.14 vs. 7.59 +/- 2.72, P = 0.027, respectively). In kidney arterioles isolated by laser capture microdissection, the ACE/ACE2 mRNA ratio was also decreased compared with control mice (1.21 +/- 0.31 vs. 4.63 +/- 0.86, P = 0.044, respectively). In conclusion, in kidney arterioles ACE2 is preferentially localized in the tunica media, and its expression is increased after administration of the angiotensin II type 1 receptor blocker, telmisartan. Amplification of ACE2 in the renal vasculature may contribute to the therapeutic action of telmisartan by increasing angiotensin II degradation.

Effects of losartan on angiotensin receptors in the hypertrophic rat heart

The effects of losartan on angiotensin receptors in hypertrophic rat hearts were studied. The study was prompted by inconsistent findings of either an increase or decrease in the mRNA of the AT1 receptor in the hearts of cardiac hypertrophic rats treated with losartan, and a paucity of information on the effects of losartan on functional angiotensin receptors in the heart. Losartan, administered i.p. to aortic coarcted rats, dose-dependently attenuated the cardiac hypertrophy. Significant effect was observed with a dose of 2.72 micromol/kg/day for four days. Hypertrophy was accompanied by an increase in [125I]-Sar1-Ile8-angiotensin II binding sites (due mainly to an increase in AT2 binding) and AT2 receptor protein in cardiac ventricles of aortic coarcted rats. Treatment with effective anti-hypertrophic doses of losartan dose-dependently downregulated the [125I]-Sar1-Ile8-angiotensin II binding sites, constitutive AT1 receptor protein, and the over expressed AT2 receptor protein. It was suggested that the anti-cardiac hypertrophic action of losartan resulted from its ability to suppress the expression of both the basal and enhanced cardiac angiotensin receptors. This raises the question as to whether such drastic action could form the therapeutic basis for the use of losartan in cardiac pathologies.

Superiority of combination of thiazide with angiotensin-converting enzyme inhibitor or AT1-receptor blocker over thiazide alone on renoprotection inl-NAME/SHR

The renal and glomerular dynamic effects of combining thiazide and angiotensin antagonists have not been reported. The present study was designed to examine the effects of hydrochlorothiazide (HCTZ) alone or in combination with an angiotensin-converting enzyme inhibitor or ANG II type 1-receptor blocker on renal hemodynamics, glomerular dynamics, renal function, and renal histopathology in the Nω-nitro-l-arginine methyl ester-treated spontaneously hypertensive rat (l-NAME/SHR) model. HCTZ (80 mg·kg−1·day−1) alone or in combination with enalapril (30 mg·kg−1·day−1) or losartan (30 mg·kg−1·day−1) or enalapril (15 mg·kg−1·day−1) plus losartan (15 mg·kg−1·day−1) was administered to l-NAME/SHR (5.0 ± 0.10 mg·kg−1·day−1) for 3 wk. Mean arterial pressure, total peripheral resistance, renal plasma flow, glomerular filtration rate, glomerular hydrostatic pressure, afferent and efferent glomerular arteriolar resistances, single nephron plasma flow, single nephron glomerular filtration rate, serum creatinine concentration, 24-h urinary protein excretion, and glomerular and arteriolar injury scores were determined. HCTZ reduced mean arterial pressure, total peripheral resistance, glomerular hydrostatic pressure, and afferent and efferent glomerular arteriolar resistances ( P < 0.05, at least) but slightly increased renal plasma flow and single nephron plasma flow associated with reduced serum creatinine concentration, urinary protein excretion, and arteriolar injury score compared with l-NAME/SHR control. However, the combination of enalapril and/or losartan with HCTZ markedly improved each of these functions. These results demonstrated minor benefits of HCTZ monotherapy and a marked superiority of its combination with enalapril and/or losartan over HCTZ monotherapy on renoprotection in l-NAME/SHR, thereby providing strong evidence of their clinical benefits for hypertensive patients with renal functional impairment.

Vasopeptidase inhibition has beneficial cardiac effects in spontaneously diabetic Goto–Kakizaki rats

In this study we examined diabetes- and hypertension-induced changes in cardiac structure and function in an animal model of type 2 diabetes, the Goto-Kakizaki (GK) rat. We hypothesized that treatment with omapatrilat, a vasopeptidase inhibitor, which causes simultaneous inhibition of angiotensin converting enzyme and neutral endopeptidase, provides additional cardioprotective effects, during normal- as well as high sodium intake, compared to treatment with enalapril, a selective inhibitor of angiotensin converting enzyme. Fifty-two GK rats were randomized into 6 groups to receive either normal-sodium (NaCl 0.8%) or high-sodium (NaCl 6%) diet and enalapril, omapatrilat or vehicle for 12 weeks. The GK rats developed hypertension, cardiac hypertrophy and overexpression of cardiac natriuretic peptides and profibrotic connective tissue growth factor compared to nondiabetic Wistar rats. The high dietary sodium further increased the systolic blood pressure, and changed the mitral inflow pattern measured by echocardiography towards diastolic dysfunction. Enalapril and omapatrilat equally decreased the systolic blood pressure compared to the control group during normal- as well as high-sodium diet. Both drugs had beneficial cardioprotective effects, which were blunted by the high dietary sodium. Compared to enalapril, omapatrilat reduced the echocardiographically measured left ventricular mass during normal-sodium diet and improved the diastolic function during high-sodium diet in GK rats. Furthermore, omapatrilat reduced relative cardiac weight more effectively than enalapril during high sodium intake. Our results suggest that both the renin-angiotensin and the neutral endopeptidase system are involved in the pathogenesis of diabetic cardiomyopathy since vasopeptidase inhibition was shown to provide additional benefits in comparison with selective angiotensin converting enzyme inhibition alone.

Haemodynamic effects of dual blockade of the renin-angiotensin system in spontaneously hypertensive rats: influence of salt

OBJECTIVE

To elucidate the mechanisms responsible for the adverse renal effects induced by dual blockade of the renin-angiotensin system (RAS) and the role of salt therein.

METHODS

The effects of enalapril, losartan and their combination on blood pressure, renal haemodynamics, renal function and RAS were investigated over a wide range of doses in spontaneously hypertensive rats fed either a low-sodium or a high-sodium diet.

RESULTS

In rats fed the low-sodium diet, the losartan-enalapril combination induced the same dose-dependent haemodynamic and hormonal changes as did three- to 10-fold greater doses of enalapril or losartan alone. When a strong decrease (> 50%) in blood pressure was achieved (with 10 mg/kg enalapril plus 10 mg/kg losartan, 100 mg/kg enalapril or 100 mg/kg losartan), a massive renal vasoplegia occurred and renal insufficiency developed. In addition, because of the huge release of renin, angiotensinogen concentrations were reduced, leading to a decrease in intrarenal angiotensins. In rats fed the high-sodium diet, those treated with the enalapril 30 mg/kg plus losartan 30 mg/kg combination, despite complete functional RAS blockade, exhibited smaller decreases in blood pressure and renal resistance, lesser release of renin and angiotensinogen consumption, and a normal renal function. These effects were similar to those produced by 100 mg/kg of enalapril or losartan in rats fed the high-salt diet, or by 10 mg/kg of enalapril or of losartan in rats fed the low-salt diet.

CONCLUSIONS

Dual RAS blockade could be either beneficial, when sodium intake is unrestricted, or dangerous, when sodium intake is restricted.

Target organ involvement in hypertension: a realistic promise of prevention and reversal

The major message from this discussion is that the end points from hypertensive disease (stroke, CHD, and hypertensive emergencies) are now preventable. Cardiac failure and ESRD, however, two exceedingly common end points from long-standing hypertension, remain as major disabilities and causes of death. The former is the most common cause of hospitalization in industrialized societies; hypertension and diabetes mellitus are the most common causes of the latter. The mechanisms of risk of these target organ diseases is not LVH per se, or the elevated arterial pressure alone in the kidney, but the coronary and renal ischemia, organ fibrosis, and, perhaps, apoptosis. Present day therapy now can effectively reverse these costly (economically and by human suffering) complications. Recent experimental studies suggest that, when used early enough, these newer pharmacologic agents may even prevent their occurrences and consequences. The very practical lesson from these experiences is that early detection and treatment of hypertension, effective control of arterial pressure, and the suppression of the underlying disease mechanisms markedly reduce the now increasing prevalence of both cardiac and renal failure.

Management of diabetic and hypertensive cardiovascular disease

The simultaneous occurrence of essential hypertension and diabetes mellitus is exceedingly common. In recent years the treatment of the cardiovascular and renal complications has not only become more specific but more effective. The evidence-based medicine data have been provided through many large multicenter studies and strongly support the promise not only of effective treatment in retarding the progression of target-organ involvement, but also the potential of reversal. These dramatic therapeutic improvements have been made possible by wedding the involved pathophysiologic disease mechanisms with the actions of pharmacologic agents. Inherent in this concept is the promise of retarding the development of the cardiovascular and renal morbid events and also reducing their associated mortal endpoints.

Omapatrilat induces profound renal vasodilation but does not affect coronary hemodynamics

BACKGROUND

Omapatrilat has potent enzymatic inhibitory effects on the angiotensin-converting enzyme and neutral endopeptidase. The prolonged effects of this inhibition on systemic and regional hemodynamics, cardiovascular mass, and hydroxyproline concentration in spontaneously hypertensive rats were studied. The contribution of endogenous bradykinin on the cardiovascular actions of omapatrilat in this genetic model of hypertension was also investigated.

METHODS AND RESULTS

Systemic and regional hemodynamics (radionuclide-labeled microspheres), left and right ventricular and aortic masses, and hydroxyproline concentration were determined in 35-week-old spontaneously hypertensive rats after 12 weeks of treatment with omapatrilat (40 mg/kg/day), with and without the bradykinin receptor antagonist icatibant (500 microg/kg/day). Omapatrilat decreased mean arterial pressure, reducing total peripheral resistance as well as decreased left ventricular and aortic mass indices. It also induced a profound renovasodilation associated with a decrease renal vascular resistance that markedly increased renal blood flow. Coronary hemodynamics and left ventricular hydroxyproline concentration remained unaltered. Concomitant blockade of bradykinin receptors partially attenuated the hypotensive effect of omapatrilat and its effect on aortic mass; and icatibant did not influence the renovasodilation.

CONCLUSION

Omapatrilat produced profoundly beneficial effects on systemic and renal hemodynamics, as well as on left ventricular and aortic masses, without any effect on coronary hemodynamics. These effects of omapatrilat on arterial pressure and aortic mass, but not on renal hemodynamics and left ventricular mass, may have been at least partially mediated through the action of bradykinin.

Cardiovascular status following combined angiotensin-converting enzyme and AT1 receptor inhibition in conscious spontaneously hypertensive rats

1. Combined treatment of spontaneously hypertensive rats (SHR) with AT1 receptor antagonists and angiotensin-converting enzyme (ACE) inhibitors has been shown to reduce mean arterial pressure (MAP) more than monotherapy with either agent. The aims of the present study were to investigate the effects of chronic dual renin-angiotensin system (RAS) inhibition using non-hypotensive doses of the AT1 receptor antagonist candesartan cilexetil and the ACE inhibitor perindopril on cardiovascular function and structure. 2. Adult male SHR, aged 15 weeks, were divided into four groups: (i) candesartan cilexetil (0.5 mg/kg per day in drinking water); (ii) perindopril (0.3 mg/kg per day in drinking water); (iii) combined treatment (dual RAS inhibition); or (iv) the appropriate vehicle (0.1% ethanol/0.1% polyethylene glycol/1.5 mmol/l sodium bicarbonate dissolved in water for candesartan cilexetil; distilled water for perindopril). Systolic blood pressure was measured weekly using the tail-cuff method and urinary microalbuminuria was measured fortnightly. 3. After 4 weeks, rats were instrumented for intravenous drug administration and measurement of MAP. At this time, the cardiovascular effects of angiotensin (Ang) I and AngII (5-20 ng) and sodium nitroprusside (SNP) and acetylcholine (ACh; 1-5 micro g) were assessed. In addition, left ventricular : bodyweight and media : lumen ratios were determined as indices of cardiac and vascular hypertrophy, respectively. 4. Candesartan cilexetil and perindopril alone had minimal effect on MAP when measured both directly and indirectly, whereas direct MAP was significantly decreased in the combined treatment group (131 +/- 6 mmHg; P < 0.05) compared with the vehicle group (156 +/- 9 mmHg). Pressor responses to AngI were significantly decreased in all groups compared with the vehicle-treated group and pressor responses to AngII were significantly decreased in the candesartan cilexetil-treated (P < 0.01) and combined treatment groups (P < 0.01) compared with the vehicle-treated group. Depressor responses to ACh and SNP were not significantly affected by any of the antihypertensive therapies compared with vehicle-treated SHR. 5. Vascular hypertrophy was significantly decreased in the candesartan cilexetil and combined groups compared with the vehicle-treated group, whereas cardiac hypertrophy was reduced, with the rank order of effect being: dual RAS inhibition > perindopril > candesartan cilexetil. Urinary albumin tended to decrease with dual RAS inhibition, but was not significantly affected by this short-term treatment. 6. These results demonstrate the efficacy of low-dose dual RAS inhibition as an antihypertensive modality, at least in SHR, not only in reducing arterial pressure, but also in improving cardiovascular structure.

Local cardiac renin-angiotensin system: hypertension and cardiac failure

In addition to the effect on arterial pressure, angiotensin II, the effector peptide of the renin-angiotensin system (RAS), exerts mitogenic and growth promoting effects on cardiac myocytes and non-myocytic elements; and both of these effects significantly contribute to the development and progression of hypertensive heart disease (HHD). The traditional concept of the RAS as a systemic, endocrine system has been expanded and the identification of its components in many organs and tissue has been amassed. This paper reviews evidence that supports the concept that the cardiac RAS participate importantly in the development and risk of HHD.

Bioenergetic remodeling of heart during treatment of spontaneously hypertensive rats with enalapril

We used spontaneously hypertensive rats to study remodeling of cardiac bioenergetics associated with changes in blood pressure. Blood pressure was manipulated with aggressive antihypertensive treatment combining low dietary salt and the angiotensin-converting enzyme inhibitor enalapril. Successive cycles of 2 wk on, 2 wk off treatment led to rapid, reversible changes in left ventricular (LV) mass (30% change in <10 days). Despite changes in LV mass, specific activities of bioenergetic (cytochrome-c oxidase, citrate synthase, lactate dehydrogenase) and reactive oxygen species (ROS) (total cellular superoxide dismutase) enzymes were actively maintained within relatively narrow ranges regardless of treatment duration, organismal age, or transmural region. Although enalapril led to parallel declines in mitochondrial enzyme content and ventricular mass, total ventricular mtDNA content was unaffected. Altered enzymatic content occurred without significant changes in relevant mRNA and protein levels. Transcript levels of gene products involved in mtDNA maintenance (Tfam), mitochondrial protein degradation (LON protease), fusion (fuzzy onion homolog), and fission (dynamin-like protein, synaptojanin-2alpha) were also unchanged. In contrast, enalapril-mediated ventricular and mitochondrial remodeling was accompanied by a twofold increase in specific activity of catalase, an indicator of oxidative stress, suggesting that rapid cardiac adaptation is accompanied by tight regulation of mitochondrial enzyme activities and increased ROS production.

Heart, aging, and hypertension

Hypertension and aging adversely affect cardiovascular system and the heart is invariably involved. Manifestations of hypertensive heart disease and of the aging heart appear similar; ventricular hypertrophy, myocardial fibrosis, and impairments in ventricular function and coronary hemodynamics characterize both conditions. However, a great deal of evidence suggests that different underlying pathophysiological mechanisms may be involved. This report discusses most recent clinical and experimental findings and focuses on the alterations in nonmyocytic elements that are a part of heart involvement. Particular attention was given to factors that are responsible for exaggerated myocardial deposition of collagen that, by itself, may be responsible for ventricular dysfunction and impaired coronary hemodynamics in hypertensive and aging hearts. Newly developed therapeutical strategies, based on the most recent experimental and clinical studies, are also discussed.

Cilazapril prevents cardiac hypertrophy and postischemic myocardial dysfunction in hyperthyroid rats

We evaluated the effects of hyperthyroidism on cardiac structural changes and postischemic myocardial function, and also studied how an angiotensin-converting enzyme (ACE) inhibitor, cilazapril, can alter these changes. Hyperthyroidism was induced by daily intraperitoneal injection of thyroxine (T4) (600 microg/kg) with or without cilazapril (10 mg/kg per day, orally), and control rats were given by vehicle. After 2 weeks of treatment, T4-treated rats showed increases in blood pressure and heart weight to body weight ratio (HW:BW). Cilazapril decreased blood pressure to control values and reduced HW:BW. In the isolated working heart preparation, T4-treated rats showed a poor postischemic recovery of left ventricular pressure-rate product (14% of baseline at 30 minutes of reperfusion vs. vehicle 85%) and cardiac work (6% vs. 71%). Cilazapril recovered both values to 49% and 43%. Propranolol (500 mg/L in drinking water) decreased blood pressure to the same extent as cilazapril in hyperthyroid rats, but changed neither HW:BW nor the postischemic myocardial dysfunction. Percent recovery of cardiac work was inversely well correlated with HW:BW (R2 = 0.998, p < 0.001). Results indicate that T4-induced cardiac hypertrophy enhances postischemic cardiac dysfunction. Results also indicate renin-angiotensin system (RAS), but not sympathetic nerve activation, is involved in cardiac hypertrophy and postischemic myocardial dysfunction in hyperthyroid rats.

Pressure-independent enhancement of cardiac hypertrophy in natriuretic peptide receptor A-deficient mice

Mice lacking natriuretic peptide receptor A (NPRA) have marked cardiac hypertrophy and chamber dilatation disproportionate to their increased blood pressure (BP), suggesting, in support of previous in vitro data, that the NPRA system moderates the cardiac response to hypertrophic stimuli. Here, we have followed the changes in cardiac function in response to altered mechanical load on the heart of NPRA-null mice (Npr1-/-). Chronic treatment with either enalapril, furosemide, hydralazine, or losartan were all effective in reducing and maintaining BP at normal levels without affecting heart weight/body weight. In the reverse direction, we used transverse aortic constriction (TAC) to induce pressure overload. In the Npr1-/- mice, TAC resulted in a 15-fold increase in atrial natriuretic peptide (ANP) expression, a 55% increase in left ventricular weight/body weight (LV/BW), dilatation of the LV, and significant decline in cardiac function. In contrast, banded Npr1+/+ mice showed only a threefold increase in ANP expression, an 11% increase in LV/BW, a 0.2 mm decrease in LV end diastolic dimension, and no change in fractional shortening. The activation of mitogen-activated protein kinases that occurs in response to TAC did not differ in the Npr1+/+ and Npr1-/- mice. Taken together, these results suggest that the NPRA system has direct antihypertrophic actions in the heart, independent of its role in BP control.

Obese female SHHF/Mcc-fa(cp) rats resist antihypertensive effects of renin-angiotensin system inhibition

Gender and obesity may influence response to pharmacological modulation of the renin-angiotensin system. We used SHHF/Mcc-fa(cp) rats to study effect of obesity and gender on the ability of an AT1 receptor antagonist to decrease blood pressure. After 2 weeks treatment with irbesartan (50 mg/kg), only lean and obese males showed significant decreases in blood pressure, while obese females were completely resistant. Lean females showed a trend toward lowering of pressure (p=0.06). However, irbesartan similarly shifted angiotensin II dose response curves to the right in all groups. Twelve weeks of irbesartan also failed to decrease blood pressure, but did significantly reduce heart weight in obese females. In untreated rats, obese females had lower plasma renin activity and serum angiotensin converting enzyme activity compared to lean males, while lean and obese females had increased urinary endothelin excretion. Despite an otherwise similar genetic background contributing to hypertension and heart failure, obese females have different patterns of humoral activation compared to lean males, which may contribute to their resistance to the depressor effects of irbesartan.

Renin-angiotensin system inhibition improves coronary flow reserve in hypertension

Angiotensin II not only elevates arterial pressure, it adversely alters hemodynamics and cardiovascular structure and exacerbates the course of hypertensive disease. Alterations in coronary hemodynamics, including reductions in coronary blood flow and flow reserve, reflect the pathophysiology of arteriolar disease and associated endothelial dysfunction thereby promoting coronary insufficiency and increasing overall cardiovascular risk. In spontaneously hypertensive rats, coronary flow reserve, the difference between basal coronary blood flow and the flow achieved during maximal coronary vasodilation achieved by physiological or pharmacological interventions, is drastically impaired at rest; however, it can be improved significantly by pharmacological agents that inhibit the renin-angiotensin system, alone or in combination. The combination of an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin-II (type 1) receptor blocker, in equidepressor doses, markedly improved coronary flow reserve to levels seen in normotensive Wistar Kyoto rats after 12 weeks of treatment, while diminishing cardiovascular mass and improving systemic hemodynamics and ventricular metabolic demands. These findings suggest the potential merits for clinical studies employing the combination of ACE inhibitor and angiotensin receptor blocker therapy in patients with hypertension and hypertensive heart disease.

Abnormal renal vascular responses to dipyridamole-induced vasodilation in spontaneously hypertensive rats

The objective of this study was to determine whether there were differences in hemodynamic responses of different vascular beds to systemic administration of dipyridamole between spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. To this end, systemic hemodynamics and organ blood flows (using labeled microspheres) were determined in conscious rats before and 10 minutes after dipyridamole (4 mg. kg(-1). min(-1)) infusion. In both the normotensive and hypertensive rats, the dipyridamole infusion reduced arterial pressure by approximately 20 mm Hg, associated with a decreased total peripheral resistance and an increased cardiac output. Renal blood flow decreased significantly in SHR after dipyridamole but remained unchanged or increased slightly in the WKY rats. There were no other differences in regional hemodynamics, including those of brain, liver, skin, and muscle, between the WKY and SHR. Antihypertensive treatment completely restored normal renal vascular response to dipyridamole. Previous reports had demonstrated an abnormal coronary hemodynamic response of the SHR. Our data demonstrate that, as with coronary hemodynamics, hypertension selectively induced alterations in renal vasculature. These findings may be of importance in identifying the earliest hemodynamic evidence of developing hypertensive nephrosclerosis.

Myocardial ischemia activates the JAK-STAT pathway through angiotensin II signaling in in vivo myocardium of rats

There have been many studies concerning the hemodynamics and physiological mechanisms in ischemic heart disease, little is known about molecular mechanisms during myocardial ischemia in in vivo study. As the signal transduction pathway responsible for myocardial hypertrophy and apoptosis, janus kinase (JAK) and signal transducers and activators of transcription (STAT) are suggested to play an important role. However, whether in vivo activation of JAK-STAT pathway occurs during myocardial ischemia is still unknown. The purpose of this study was to determine whether myocardial JAK or STAT is activated in ischemic heart, and to evaluate the angiotensin blockade on the pathway. Myocardial infarction was produced by ligation of the coronary artery in Wistar rats. After myocardial ischemia, we analysed both activated levels and total amounts of JAK1, JAK2, STAT1 and STAT3 by Western blot analyses at 0, 5, 15, 30, 60, 120 and 240 min. Compared with JAK activities at 0 min, JAK1 activities were significantly increased at 60 and 120 min (3.0- and 3.7-fold, respectively, P<0.01). JAK2 and STAT1 activities of ischemic myocardium were unchanged through the time course. STAT3 activities were increased at 5 min (3.3-fold, P<0.01) and markedly enhanced at 30, 60 and 120 min (4.6-, 7.7- and 8.7-fold, respectively, P<0.01). Pretreatment with imidapril (ACE inhibitor) and candesartan cilexitil (AT1 receptor antagonist) significantly prevented the increase in the phosphorylation of JAK1 at 120 min and STAT3 at 30 and 120 min. Sis-inducing factor (SIF) DNA complex was supershifted by specific anti-STAT3 antibody, indicating that increased SIF complex at least contained activated STAT3 proteins in ischemic myocardium. Imidapril and candesartan cilexitil inhibited the activation of SIF DNA binding at 1 day after coronary ligation. In conclusion, we showed that JAK1 and STAT3 were activated by ischemia from the basal activities in in vivo rat myocardial ischemia model. Imidapril and candesartan cilexitil prevented the increase in phosphorylated JAK1 and STAT3, thereby suggesting that angiotensin II, especially angiotensin II type I receptor, partially mediates activation of myocardial JAK-STAT pathway in acute myocardial ischemia.

Hypertension and the heart

Sustained increase in arterial pressure causes left ventricular hypertrophy and adversely affects all myocardial compartments: myocytes, interstitium, and coronary vasculature. Ventricular hypertrophy significantly increases the risk for cardiovascular morbidity and mortality in hypertensive disease. Impairments in coronary circulation and ventricular fibrosis, which are an essential part of hypertensive disease, contribute to that increased risk. This report discusses the mechanisms of hypertension-induced myocardial collagen accumulation and impairments in coronary hemodynamics. Particular attention is given to the interaction of hypertension and aging because aging aggravates hypertensive changes and the incidence of hypertension increases with aging. The effect of therapy on hypertension-induced ventricular fibrosis and impairment in coronary hemodynamics and the risk associated with these changes are also discussed.

Pilot study of combined blockade of the renin-angiotensin system in essential hypertensive patients

BACKGROUND

Additive hemodynamic effects of combined blockade of the renin-angiotensin system by an angiotensin I converting enzyme inhibitor and an angiotensin II antagonist have been observed in sodium-depleted normotensive volunteers and in patients with congestive heart failure.

OBJECTIVE

To investigate whether the same additive hemodynamic effects occur in patients with hypertension and to verify the safety of such an approach.

DESIGN

Multicenter, randomized, double-blind, parallel-group, pilot study.

PATIENTS

177 patients with mild-to-moderate hypertension [diastolic blood pressure (DBP): 95-115 mmHg after a 4-week placebo run-in period] were included in the study.

INTERVENTION

Combination therapy consisting of 50 mg losartan daily and 10 mg enalapril daily was administered for 6 weeks. The effects of this therapeutic regimen was compared with similar groups of patients who received either 50 mg losartan daily or 10 mg enalapril daily.

MAIN OUTCOME MEASURES

24-hour ambulatory mean DBP and clinic DBP measured at trough after 6 weeks of treatment.

RESULTS

24-hour ambulatory mean DBP did not significantly differ between treatment groups although the combination tended to lower BP more. The combination therapy was more effective on clinic DBP measured at trough than was losartan by 3.2 mmHg [confidence interval (95%, CI) 0.7-5.7 mmHg, P = 0.012], and more effective than enalapril by 4.0 mmHg (95% CI, 1.5-6.4 mmHg, P = 0.002). In a subgroup of 28 patients, higher plasma active renin and angiotensin I levels during blockade by the combination therapy were observed. This finding confirmed that the combination of the two agents inhibited the renin-angiotensin system to a greater extent than did either agent alone.

CONCLUSION

A combination of 10 mg enalapril daily and 50 mg losartan daily safely induces a supplementary, although modest, fall in clinic DBP in patients with mild-to-moderate essential hypertension.

Ischemia and fibrosis: the risk mechanisms of hypertensive heart disease

Mechanisms underlying risk associated with hypertensive heart disease (HHD) and left ventricular hypertrophy (LVH) are discussed in this report and provide a rationale for understanding this very common and important cause of death from hypertension and its complications. Emphasized are impaired coronary hemodynamics, endothelial dysfunction, and ventricular fibrosis from increased collagen deposition intramurally and perivascularly. Each is exacerbated by aging and, perhaps, also by increased dietary salt intake. These functional and structural changes promote further endothelial dysfunction, altered coronary hemodynamics, and diastolic as well as systolic ventricular contractile function in HHD. The clinical endpoints of HHD include angina pectoris (with or without atherosclerosis of the epicardial coronary arteries), myocardial infarction, cardiac failure, lethal dysrhythmias, and sudden death. The major concept to be derived from these alterations is that not all that is clinically recognized as LVH is true myocytic hypertrophy and structural remodeling. Other major co-morbid changes occur that serve to increase cardiovascular risk including impaired coronary hemodynamics, endothelial dysfunction, and ventricular fibrosis.

Therapeutic implications of escape from angiotensin-converting enzyme inhibition in patients with chronic heart failure

The level of inhibition of the angiotensin-converting enzyme (ACE) provided by standard doses of ACE inhibitors may only be partial during long-term treatment in patients with severe chronic heart failure (CHF). Partial ACE inhibition with time is often referred to as escape from ACE inhibition and labeled ACE escape. Several lines of evidence suggest that ACE escape occurs in patients with severe CHF. Plasma levels of angiotensin II rise above initial values during long-term ACE inhibition, and the effects of ACE inhibitors on cardiac remodeling and lowering of sympathetic nervous system activity attenuate after 1 year of treatment. Moreover, angiotensin II type I receptor blockade (ARB) produces clinical and hemodynamic benefits in patients with CHF who are already receiving ACE inhibitors. The therapeutic implications of ACE escape include evaluation of higher- than-standard doses of ACE inhibitors and routine addition of ARB to ACE inhibition in patients with severe CHF. Data are reviewed to demonstrate that ACE escape reflects inadequate ACE dosage rather than a decrease in ACE inhibition occurring with time.

The necessity for recognition and treatment of patients with "mild" hypertension

A dramatic evolution has occurred in the past four decades in our underlying knowledge of pathophysiology of the hypertensive diseases and in the availability of myriad pharmacologic agents for control of hypertension. This report provides a current review of antihypertensive treatment interspersed with personal opinions supported by appropriate references. It focuses on the recent national recommendations dealing with the prevention, detection, evaluation and treatment of the disease (JNC-6). Whereas I believe that the height of arterial pressure is of primary importance, it is not the sine qua non explaining all target organ involvement or complications of hypertensive disease. Consequently, all that is classified today as Stages 1 and 2 hypertension (old terminology: "mild" and "moderate") in terms of blood pressure elevation does not explain all outcomes of disease. Indeed, JNC-6 introduced the new concept of risk stratification for therapy based not only on the height of systolic and diastolic pressure but also on the presence of target organ involvement, comorbidity and other risk factors. However, after considerable advances since the inception of the National High Blood Pressure Education Program (NHBPEP) in 1972, it appears that we are avoiding our responsibilities and reversing our gains. It is of vital importance that we renew our efforts to identify, evaluate and treat all patients with hypertension; this is especially so for the vast numbers of patients with Stages 1 and 2 hypertension.

Left Ventricular Hypertrophy

The presence of left ventricular hypertrophy (LVH) as a treatable entity is of particular importance in patients with primary hypertension. Because LVH is associated with a strong risk of adverse clinical events (eg, heart failure, ischemic events, and cardiovascular death) and because evidence from retrospective studies suggests that regression of LVH, along with a decrease in blood pressure, may help modify these outcomes, the use of antihypertensive agents that have been shown to promote regression of LVH has been recommended. These include diuretics, beta-blockers (except those with intrinsic sympathomimetic activity ), angiotensin-converting enzyme (ACE) inhibitors, calcium channel blockers, peripheral alpha(1)-blockers, and central alpha(2)-stimulators. Agents to be avoided include direct arterial vasodilators (eg, hydralazine and minoxidil), which have strong sympathetic stimulating properties and tend to maintain LVH despite lowering blood pressure. The use of ACE inhibitors is increasing. Unfortunately, the cost of these agents is higher than that of some other classes of agents, such as diuretics, which show excellent evidence of regression of hypertrophy. African-American and elderly persons, in particular, may benefit from diuretics for treatment of hypertension as well as reduction of left ventricular (LV) mass. Beta-blockers should be considered in the elderly, especially those with greatly thickened LV walls and small chamber sizes, factors associated with hyperdynamic systolic performance, systolic midcavity obliteration, and diastolic relaxation abnormalities on echocardiography. Calcium channel blockers may also be useful in patients with LVH who have normal systolic performance and diastolic compliance abnormalities. The purpose of serial echocardiographic studies in patients already being treated for hypertension is to ensure that LV geometry has not worsened and that function is unchanged or improved (especially with respect to previously noted diastolic Doppler inflow abnormalities). Considerable changes in estimated LV mass (>60 g on serial intrapatient evaluation) are needed before the clinician can conclude with confidence that LV mass has decreased. More specific definitive recommendations based on the outcomes of current large-scale clinical trials are awaited.

Pharmacologic agents on cardiovascular mass, coronary dynamics and collagen in aged spontaneously hypertensive rats

OBJECTIVE

To determine whether antihypertensive treatment could alter hypertension and age-related progressive impairment of coronary hemodynamics and cardiac fibrosis in aged spontaneously hypertensive rats (SHR).

DESIGN

Old SHR were given their respective therapy for 3 months. To differentiate between hypertension and age-related changes, a comparison was made between left and right ventricular indices since the right ventricle was not exposed to pressure overload.

METHODS

Male, 65-week-old spontaneously SHR were divided into three groups and were given either vehicle, felodipine (30 mg/kg per day) or enalapril (30 mg/kg per day). After 12 weeks of the respective treatments, systemic and coronary hemodynamics (radionuclide-labelled microspheres), right and left ventricular and aortic mass indices, and right and left ventricular hydroxyproline concentrations (an estimate of collagen) were determined.

RESULTS

Arterial pressure and total peripheral resistance were reduced to the same extent in SHRs treated with either felodipine or enalapril; however, compared to the control rats, enalapril was more effective in reducing left ventricular and aortic mass indices. Both agents also improved coronary hemodynamics of both ventricles in aged SHR but enalapril was more effective as indicated by a greater increase in coronary flow reserve and a greater decrease in minimal coronary vascular resistance. Furthermore, enalapril but not felodipine reduced left ventricular hydroxyproline concentration; and right ventricular hydroxyproline concentration increased with felodipine but remained unchanged with enalapril.

CONCLUSIONS

Both enalapril and felodipine ameliorated adverse cardiovascular effects of hypertension in the aged SHRs within 12 weeks, as demonstrated by reduced arterial pressure, diminished left ventricular mass, and improved coronary hemodynamics. Enalapril also decreased aortic mass and left ventricular collagen concentration and appeared to be more effective in improving coronary hemodynamics than felodipine, possibly as a result, in part, of reduced myocardial fibrosis.

How do angiotensin II receptor antagonists affect blood pressure?

The renin-angiotensin system (RAS) plays an important role in the regulation of blood pressure. Angiotensin II is the principal effector hormone in the RAS, causing vasoconstriction and increased sodium and water retention, leading to increased blood pressure. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists both inhibit the actions of angiotensin II. ACE inhibitors prevent the formation of angiotensin II from angiotensin I, whereas angiotensin II receptor antagonists inhibit the final crucial step of angiotensin II binding with the AT1 receptor site. This article discusses the efficacy of angiotensin II receptor antagonists and their possible role in organ protection.

Non-peptide angiotensin type 1 receptor antagonists in the treatment of hypertension

Angiotensin II (Ang II) acts at the cellular level on two receptor subtypes: the AT1 receptor which can be blocked by losartan and its analogues (the 'sartan family'), and the AT2 receptor that does not react with the above antagonists but which can be blocked by different compounds, such as PD123319. AT1 receptor blockade has proven to be a highly effective means of interference with the renin-angiotensin system (RAS) and hence of reducing high blood pressure. As a result of the terminal blockade of the RAS cascade, circulating Ang II levels tend to rise two- to threefold. The free access of such enhanced levels to uninhibited AT2 receptors may be clinically relevant, as argued in the present review. The most extensive experimental and clinical experience with AT1 receptor blockade so far has been obtained with the pioneer drug losartan, although major contributions have also been made on candesartan cilexetil, irbesartan and valsartan. All of these four drugs have been instrumental in substantial clinical trials, serving as sources of information in the clinically oriented part of this review. AT1 receptor blocking drugs generally provide a relatively gradual decrease in blood pressure, which is comparable to that obtained with conventional anti-hypertensive drugs. Clinical trials reveal an astounding lack of drug-related adverse effects, scoring even better than placebo in terms of frequencies and sometimes patterns. The trough/peak ratio on single dosages seems to have been mastered, particularly with the second generation of AT1 receptor blockers, as is evident from 24 h ambulatory blood pressure monitoring. Combination with low-dose thiazide regimens is well established. Intermediate endpoints (micro-albuminuria and left ventricular hypertrophy) appear to be controllable. Morbid cardiovascular sequelae are currently under study in comparison with beta- and calcium channel blockade.

Practical considerations of the pharmacology of angiotensin receptor blockers

A review of the drug class of angiotensin receptor blockers (ARBs) as well as the ARBs currently available by prescription in the United States is presented. The importance of angiotensin II production by non-angiotensin-converting enzyme (non-ACE) pathways, particularly human chymase, is discussed. Emphasis is placed on the mechanism of action of ARBs and the different binding kinetics of these agents. Although all ARBs, as a group, block the AT1 receptor, they may differ in the pharmacological characteristics of their binding and be classified as either surmountable or insurmountable antagonists. Mechanisms of surmountable and insurmountable antagonism as well as possible benefits of these blocking characteristics are discussed in relation to the various ARBs. The cardiovascular effects of activation of the two main subtypes of angiotensin receptors (AT1 and AT2) are presented. In addition to their treatment of hypertension, ACE inhibitors are recognized as being effective in the management of heart failure, left ventricular hypertrophy, recurrent myocardial infarctions, and renal disease. ARBs are currently indicated only for the treatment of hypertension; however, in vitro and in vivo pharmacological studies as well as preliminary clinical data suggest that ARBs, like ACE inhibitors, may also provide effective protection against end-organ damage in these conditions.

Effect of long-term eprosartan versus enalapril antihypertensive therapy on left ventricular mass and coronary flow reserve in stage I-II hypertension. Eprosartan Study Group

A double-blind comparator study was performed in 528 hypertensive patients [baseline sitting diastolic blood pressure (SitDBP) 95-114 mmHg]. The primary objective was to compare the incidence of drug-related cough in patients treated with enalapril and eprosartan. This paper reports the results of 27 asymptomatic patients who were recruited into a single centre substudy of the multicentre trial and randomised to receive either eprosartan (200-300 mg b.i.d.) or enalapril (5-20 mg o.d.). Blood pressure (BP) reduction, left ventricular (LV) mass regression and change in coronary flow reserve (CFR) after 6 months' treatment with either eprosartan or enalapril were compared. At the end of the study, eprosartan and enalapril were found to have caused similar reductions in BP. There was an increase in CFR in the eprosartan group to 1.6 +/- 0.3 and a decrease in CFR in the enalapril group to 1.3 +/- 0.3. Neither value was significantly different from baseline although the difference between the two groups was significant (p = 0.05). By study endpoint, there was a significant reduction in LV mass in the enalapril group (p = 0.05), but not the eprosartan (p = ns) group. Further investigation of the effects of angiotensin receptor blockers on CFR and LV mass regression appear warranted.

Current clinical pathophysiologic considerations in essential hypertension

Over the years, much has been learned from unraveling the pathophysiological alterations associated with the hypertensive diseases. Despite this large base of fundamental and clinical information, our knowledge continues to expand. This article discusses the multifactorial nature of hypertensive disease, including the vascular and cardiac participation in the elevation of arterial pressure and in target organ involvement by the disease. Some of the most exciting advances of the last decade are summarized in this review.