Ageing, hypertension and the kidney: new data on an old problem.
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Age Factors↗
Biomedical subjects
Edward D Frohlich
Publications and source records attributed to Edward D Frohlich.
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.
Angiotensin-Converting Enzyme Inhibitors↗
Echocardiographic measurement of cardiac output in rats.
The systematic evaluation of different transthoracic echocardiographic (TTE) methods to determine cardiac output (CO) and the effect of changes in intravascular volume on echocardiographically determined indexes of cardiovascular structure in the rat has not been documented. With the use of 11 Wistar rats, simultaneous echocardiographic and thermodilution measurements of CO were compared at baseline and after blood withdrawal or transfusion at 43 different levels of intravascular volume and using 10 different echocardiographic approaches. The best correlation (r = 0.93; P < 0.0001), least bias (-3 ml/min), and best precision (16 ml/min) between thermodilution and echocardiographic methods were obtained at the level of aortic annulus using pulsed Doppler. In conclusion, CO could be accurately assessed in rats using TTE and pulsed Doppler at the level of the aortic annulus. This annulus was demonstrated to remain stable, but pulmonary annulus, thoracic aorta, mitral valve, and left ventricular diameters were found to be more modifiable during volumic changes.
Animals↗
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.
Aldosterone↗
Diastolic dysfunction in hypertension.
Heart failure is one of the most common causes of cardiovascular morbidity and mortality, and hypertension is the most common cause of cardiac failure. Recent studies have shown that isolated diastolic dysfunction very often accompanies hypertensive heart disease. Ventricular diastolic function may be divided into an active relaxation phase and a passive compliance period. These two components have been investigated invasively, and they remain the gold standards for the study of diastolic function. However, in the routine clinical setting, echocardiographic and Doppler techniques are most useful for evaluating ventricular filling. Thus, analysis of E and A waves of mitral flow have provided important and useful information. Unfortunately, these indices depend on too many factors. Newer indices obtained from ventricular time intervals, tissue Doppler imaging, and color M-mode echocardiography have enhanced the means to assess diastolic function. In addition, new methods including MRI and cine CT have also provided better understanding of left ventricular filling in hypertension. Using these techniques, diastolic dysfunction has been found to be common in patients with hypertension, even before left ventricular hypertrophy is demonstrable and before hypertension in young, normotensive male offspring of hypertensive parents has developed. Furthermore, it has been made clear recently that myocardial ischemia and fibrosis are two important factors associated with diastolic dysfunction in hypertension.
Diastole↗
Prevention of hypertension.
Hypertension is a major risk factor for many cardiovascular diseases including stroke, coronary heart disease, cardiac failure, and endstage renal disease. Therefore, prevention of hypertension becomes an important goal in overall efforts to control blood pressure and reduce the incidence of hypertension-related cardiovascular and renal complications and outcomes. Many risk factors underlying hypertension have been identified including nonmodifiable factors such as age, gender, genetic factors, and race, as well as modifiable factors including overweight, high sodium intake, low potassium intake, alcohol consumption, and reduced physical activity. A number of studies have demonstrated that interventions aimed at changing these modifiable factors might decrease blood pressure and even prevent the development of hypertension. Thus, present national recommendations and guidelines include lifestyle modifications ranging from weight loss in case of obesity, engagement in regular isotonic physical activity, reduced sodium diet (<100 mmol/d), supplementation of potassium, and alcohol moderation (<1 ounce of ethanol or its equivalent per day).
Aging↗
Cilnidipine improves spontaneously hypertensive rat coronary hemodynamics without altering cardiovascular mass and collagen.
OBJECTIVE: The present study was designed to determine the effects of prolonged treatment with cilnidipine, a novel dihydropyridine calcium antagonist which blocks both L-type and N-type calcium channels, on systemic, regional and coronary hemodynamics, cardiovascular mass and collagen content in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. METHODS: Male 23-week-old WKY and SHR rats were divided into two groups for each strain. One group received cilnidipine (10 mg/kg per day), whereas their respective controls were given no therapy. Systemic and regional hemodynamics (radionuclide-labeled microspheres), left and right ventricular and aortic mass, and hydroxyproline concentration were determined after 12 weeks treatment. RESULTS: The data demonstrated that cilnidipine neither affected systemic hemodynamics nor cardiovascular mass and collagen content in WKY rats. The same treatment in the SHR reduced arterial pressure and total peripheral resistance without changes in heart rate and cardiac index. Ventricular and aortic mass indices as well as ventricular collagen content remained unchanged. There were no differences in organ blood flows between two SHR groups, whereas renal, liver and left ventricular coronary vascular resistances were reduced by cilnidipine. After dipyridamole infusion left ventricular minimal coronary vascular resistance decreased further in cilnidipine-treated SHR as compared with control SHR rats. CONCLUSION: These data suggest that cilnidipine, an L- and N- type calcium channel antagonist, exerted beneficial effects on coronary hemodynamics without altering cardiovascular mass or collagen content in SHR.
Animals↗
N- and L-type calcium channel antagonist improves glomerular dynamics, reverses severe nephrosclerosis, and inhibits apoptosis and proliferation in an l-NAME/SHR model.
OBJECTIVE: To determine the responses of the new dihydropyridine N- and L-type calcium antagonist, cilnidipine, on systemic and renal hemodynamics, glomerular dynamics, renal function, and histopathology in an Nomega-nitro-l-arginine methylester spontaneously hypertensive rat (l-NAME/SHR) model of nephrosclerosis. METHODS: Five groups of 20-week-old male SHR were studied using renal micropuncture techniques and histopathological analyses: group 1, control; group 2, cilnidipine (10 mg/kg per day) by gavage, for 3 weeks; group 3, l-NAME (50 mg/l) in drinking water, for 3 weeks; group 4, combination of l-NAME and cilnidipine, for 3 weeks; group 5, l-NAME for 3 weeks, followed by cilnidipine for a subsequent 3 weeks. RESULTS: Cilnidipine significantly reduced mean arterial pressure, total peripheral resistance and renal vascular resistance, while increasing effective renal blood flow and glomerular filtration rate (P < 0.01) in l-NAME/SHR. These hemodynamic changes were associated with significantly increased single nephron glomerular filtration rate (SNGFR) and plasma flow (SNPF) and decreased afferent glomerular arteriolar resistances when cilnidipine was used alone, and with increased SNGFR and SNPF, but decreased glomerular capillary pressure, afferent and efferent arteriolar resistances, urinary protein excretion, serum creatinine and uric acid concentrations (at least P < 0.05) in l-NAME-exacerbated SHR nephrosclerosis. In addition, glomerular and arteriolar injuries were markedly reversed (both P < 0.01), and glomerular apoptosis and cellular proliferation were inhibited and associated with glomerular tuft enlargement and an increase in cell number. CONCLUSION: Cilnidipine not only prevented, but reversed, the severe renal hemodynamic and glomerular dynamic changes, including apoptosis and glomerular cellular proliferation, in l-NAME/SHR-exacerbated nephrosclerosis. This dual-channel calcium antagonist thus exerted renoprotective pathophysiological effects in the l-NAME/SHR.
Animals↗
High rate of ventricular septal defects in WKY rats.
In 1979, we first reported occurrence of biventricular hypertrophy in the original normotensive Wistar-Kyoto (WKY) strain obtained from the National Heart, Lung, and Blood Institute, which was derived directly from the Kyoto laboratory of Okamoto. At that time, we recommended that both ventricles be weighted when WKY are studied so that invalid conclusions are not made. Because no paper confirmed these findings for almost 20 years, heart weights were reported in only a few WKY studies, and the cause of this biventricular hypertrophy remained unknown, we re-evaluated this problem in commercially available rats. We, therefore, investigated WKY rats using transthoracic echocardiography to define the congenital heart defect. Up to 28% of commercially available WKY rats demonstrated severe congenital cardiac abnormalities associated with biventricular hypertrophy. Ventricular septal defect with pulmonary regurgitation was the most commonly encountered cardiac defect; other abnormalities included patent ductus arteriosus, and valvular defects. Pathologic and invasive hemodynamic studies confirmed these echocardiographic findings. Because this defect occurs in a large number of WKY rats obtained commercially from 2 different sources, investigators using this strain must carefully measure both ventricular weights to be certain that inappropriate and invalid conclusions are not derived therefrom.
Animals↗
Clinical management of the obese hypertensive patient.
Despite years of investigation our fundamental and clinical knowledge of the major public health problem, obesity-hypertension, is relatively meager and certainly inadequate. We are at a loss to explain why the pathophysiological mechanisms of obesity and hypertension are so inextricably intertwined. Adding to this frustration is the inadequacy of the treatment for obesity. Hemodynamically, we recognize that the expanded plasma volume caused by obesity imparts a significant volume overload on the heart, thereby increasing cardiac output, while the hypertension compounds this ventricular stress by an associated pressure overload. Thus, the ventricle has an eccentric as well as a concentric adaptive hypertrophy. Associated with obesity is an increased burden of pressor (e.g., catecholamine, angiotensin II); peptide (e.g., endothelin, insulin, leptin, natriuretic); hormonal (e.g., growth, steroids, thyroid); and neural mechanisms. Further complicating these alterations are electrolytic, lipid, uric acid, and other metabolic factors. Both diseases (obesity and hypertension) are exacerbated by frequently encountered comorbid pathophysiological disorders including atherosclerosis, ventricular dysfunction, diabetes mellitus, hyperlipidemias, and sleep apnea. To add to these issues, therapy for obesity-hypertension is suboptimal. Behavioral modification (of overweight and obesity) is commonly characterized by recidivism, and pharmacotherapy of obesity is woefully inadequate; the present agents either raise arterial pressure or are fraught with adverse effects. Fortunately, there are no contraindications imparted by obesity that complicate the drug treatment of the associated hypertension. Each of the lifestyle modifications and seven classes of antihypertensive therapy that is discussed herein is done in light of the coexistent hypertension and comorbid diseases.
Angiotensin-Converting Enzyme Inhibitors↗
Seasonal variations in blood pressure.
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Aged↗
Edward D. Frohlich, MD. A conversation about hypertension: from bedside to bench and return. Interview by Hector O. Ventura.
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Cardiology↗