Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0018801 (heart failure)
 72,216 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The increase in norepinephrine (NE) blood levels in human heart failure correlates with prognosis. In this study, we determined whether continuous NE infusion alters the positive inotropic and chronotropic responses of isolated rat cardiac muscles. Osmotic minipumps were implanted subcutaneously (s.c.) in 43 adult male rats to deliver NE (160 micrograms/kg/h for 14 days); 42 rats were sham-operated. Isolated left and right atria and left and right ventricular (LV, RV) papillary muscles were prepared to measure positive inotropic or chronotropic responses to NE, phenylephrine, forskolin, dibutyryl cyclicAMP (dbcyclicAMP), and calcium chloride. NE infusion caused (a) a 22% increase in LV wet weight without altering atrial or RV wet weights; (b) an 18% decrease in maximal inotropic response to calcium chloride in LV papillary muscles only; (c) a significantly decreased peak response to NE [72 +/- 5 vs. 93 +/- 5% (sham rats) of calcium chloride] but not to forskolin or dbcyclicAMP in RV papillary muscles; (d) an increased incidence of ectopy at low concentrations of NE, forskolin, and dbcyclicAMP in LV papillary muscles; (e) no alteration in papillary muscle responses to phenylephrine but significantly increased left atrial inotropic responses [51 +/- 5 vs. 33 +/- 2% (sham rats) of calcium chloride] and right atrial chronotropic responses [30 +/- 2 vs. 18 +/- 4 (sham rats) beats/min]; and (f) a selective decrease in beta 1-adrenoceptor density in both ventricles. Thus, NE infusion causes selective LV hypertrophy; responses of compounds that increase intracellular cyclicAMP are affected to a greater extent in papillary muscles from the hypertrophied ventricle than in tissues from the other chambers of the heart.
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PMID:Cardiac responses after norepinephrine-induced ventricular hypertrophy in rats. 138 Oct 25

Treatment of male rabbits with adriamycin at a cardiotoxic dose (1 mg/kg intravenously, i.v., twice a week for 9 weeks) caused cardiovascular disturbances characteristic of chronic heart failure. The severity of symptoms varied, indicating differences in the individual sensitivity of the animals to adriamycin. Thus, cardiac output (CO) was decreased by greater than 40% in only 4 of the 7 animals in which it was measurable at 9 weeks. Elevated levels of atrial natriuretic factor (ANF) and plasma renin activity (PRA), as well as pulmonary congestion, hydrothorax, and ascites were also evident. The baroreflex response to sodium nitroprusside (NPS) was blunted. The response to the inotropic drug dobutamine was depressed by 50% as compared with the control animals. Right ventricular beta-adrenoceptor density was significantly reduced in these animals (22.9 +/- 3.1 as compared with 31.8 +/- 1.0 fmol/mg protein in control animals) owing to a selective downregulation of the beta 1-adrenoceptor population. The loss of beta-adrenoceptors was highly correlated with severity of heart failure symptoms: i.e., baroreflex dysfunction as indicated by the NPS slope (r = 0.91), decrease in CO during the previous weeks (r = 0.88), and plasma norepinephrine (NE) levels (r = 0.96). However, when all adriamycin-treated animals were compared collectively regardless of the severity of heart failure, with the controls, no difference in the beta-adrenoceptor density was detectable, a finding in agreement with previous observations in this model. Chronic treatment of rabbits with adriamycin thus causes low-output failure, reflecting some of the findings reported for the human disease; however, individual sensitivity to adriamycin varies considerably between rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Chronic adriamycin treatment and its effect on the cardiac beta-adrenergic system in the rabbit. 138 76

Most positively inotropic drugs are available only as intravenous injection, which restricts their use in chronic heart failure. A single and brief infusion of dobutamine--a synthetic catecholamine and potent beta 1-adrenoreceptor agonist--provides a clinical improvement which may last for several weeks. On the other hand, tachyphylaxis to dobutamine may develop after a several days' infusion, so that the drug gradually loses its effectiveness. In patients with chronic heart failure, intermittent infusions of dobutamine result in sustained clinical improvement in more than 50 percent of the cases. The relative preservation of beta-adrenoceptors seems to play a role in the beneficial effects of intermittent infusions. The most significant side-effects of dobutamine are ventricular rhythm disorders. The practical applications and supervision of repeated dobutamine infusions in chronic heart failure are detailed.
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PMID:[Treatment of chronic heart insufficiency with dobutamine. Value and limitations]. 148 May 69

Although blunted cardiac response to sympathetic stimulation in patients with heart failure is usually attributed to myocardial beta 1-adrenoceptor downregulation secondary to elevated circulating catecholamines, cardiomegaly per se may also play a role through presynaptic mechanisms such as reduction in cardiac norepinephrine (NE) concentration. To evaluate effects of cardiac dilatation on cardiac response to sympathetic stimulation, we studied left ventricular contractile and heart rate responses to plasma NE levels increased by exercise in 10 asymptomatic patients with a dilated left ventricle due to aortic regurgitation (AR), but with normal resting plasma NE levels, using 10 normal subjects and 10 patients with heart failure due to dilated cardiomyopathy (DCM) as controls. Plasma NE levels, systemic blood pressure, echocardiographic left ventricular dimensions, and heart rate were measured at rest, and at 3 submaximal levels of supine bicycle exercise. The ratio of peak systolic blood pressure to end-systolic dimension (P/D ratio), heart rate, and plasma NE increased with the intensity of exercise. In each subject, both P/D ratio and heart rate increased in a logarithmic manner against plasma NE levels. The slope of the regression line for log (plasma NE)--P/D ratio relation, and that for log (plasma NE)--heart rate relation, were significantly less in patients with AR than in normal subjects (p less than 0.001 and p less than 0.05, respectively), and were less in patients with DCM than in patients with AR (p less than 0.005 and p = 0.051, respectively). Thus, the left ventricular contractile and heart rate responses to sympathetic stimulation are blunted in patients with dilated hearts due to AR, even in the absence of overt heart failure and elevated plasma NE levels. These responses were further decreased in patients with heart failure due to DCM. Cardiac responses to sympathetic stimulation appear to be blunted by cardiac dilatation per se, independently of myocardial beta 1-receptor downregulation secondary to high circulating catecholamines. The decrease in mechanical response to sympathetic stimulation in failing hearts is likely to be combined result of cardiac dilatation and beta 1-receptor downregulation.
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PMID:Blunted cardiac responses to exercise-induced sympathetic stimulation in non-failing aortic regurgitation: insight into role of cardiac dilation in hyporesponse of failing hearts. 154 33

In patients with congestive heart failure, down-regulation of beta-adrenoceptors is present, probably as a result of sympathetic overstimulation. In end-stage dilated cardiomyopathy, beta 1-adrenoceptor density is markedly reduced, while beta 2-adrenoceptor density is normal. This latter finding does not necessarily imply normal sensitivity to beta 2-stimulation, due to possible alterations in the beta-adrenoceptor/adenylate cyclase complex beyond the receptor. In some disease states, such as ischemic cardiomyopathy and mitral valve disease, there seems to be a concomitant reduction of the beta 1- and beta 2-adrenoceptor density. The finding of beta-adrenoceptor down-regulation has stimulated the search for novel therapeutic approaches in heart failure patients. Beta-agonists could even further down-regulate beta receptors, and this perhaps explains why they seem not to be useful in long-term use. Agents that directly stimulate adenylate cyclase activity, such as forskolin, or that increase cyclic adenosine monophosphate degradation, such as the phosphodiesterase inhibitors, are being tested. Beta-adrenoceptor blocking agents were used in treatment of heart failure before beta-adrenoceptor down-regulation was recognized in these patients. It is tempting to speculate that the beneficial clinical and hemodynamic effects seen in these patients treated with metoprolol is indeed due to an antagonism of the beta-adrenoceptor down-regulation. Studies testing whether beta-adrenoceptor blocking agents can improve survival in congestive heart failure patients are on-going.
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PMID:Receptor function in heart failure. 164 66

Cardiac beta-adrenoceptor density and beta 1- and beta 2-subtype distribution were examined in human left ventricular myocardium from transplant donors serving as controls and from patients with mitral valve stenosis, aortic valve stenosis, idiopathic dilated cardiomyopathy, and ischaemic cardiomyopathy respectively. The total beta-adrenoceptor density was similar in transplant donors and patients with moderate heart failure (NYHA II-III) due to mitral valve stenosis, but was markedly reduced in all forms of severe heart failure (NYHA III-IV) studied. A reduction of both beta 1- and beta 2-adrenoceptors was found in patients with severe heart failure due to mitral valve stenosis or ischaemic cardiomyopathy. In contrast, a selective down-regulation of beta 1-adrenoceptors with unchanged beta 2-adrenoceptors and hence a relative increase in the latter was observed in idiopathic dilated cardiomyopathy and aortic valve stenosis. It is concluded that the extent of total beta-adrenoceptor down-regulation is related to the degree of heart failure. Selective loss of beta 1-adrenoceptors is not specific for idiopathic dilated cardiomyopathy but also occurs in aortic valve stenosis. Changes in beta 1- and beta 2-subtype distribution are rather related to the aetiology than to the clinical degree of heart failure.
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PMID:Distinct down-regulation of cardiac beta 1- and beta 2-adrenoceptors in different human heart diseases. 164 74

During a 3-year period we administered enoximone, a phosphodiesterase inhibitor with positive inotropic and vasodilator properties, to 73 pretransplantation patients with end-stage heart failure who exhibited a clinical requirement for additional inotropic support. The clinical course and myocardial beta-adrenergic receptor status in the explanted hearts of these 73 patients was compared with results in 113 concurrently listed pretransplantation patients not requiring additional inotropic support. Only three patients required cessation of enoximone because of adverse effects, all from exacerbation of ventricular arrhythmias. Sixty-six of 73 (90.4%) enoximone-treated patients ultimately underwent cardiac transplantation a mean of 39.2 +/- 6.6 days (range 1 to 221 days) after starting enoximone, whereas seven patients (9.6%) died awaiting cardiac transplantation. The respective 1-, 3-, and 6-month pretransplantation survival rates of patients treated with enoximone calculated from their time on the waiting list for transplantation were 88.0%, 82.5%, and 82.5% compared with 92.1%, 83.8%, and 76.2% in control patients not receiving enoximone (all p = not significant). In 25 patients who received enoximone, ventricular myocardial beta-adrenergic receptors were measured at the time of transplantation and compared with values in failing ventricles from 52 pretransplantation patients not exposed to enoximone. Compared with ventricular myocardium of patients not given enoximone or intravenous beta-adrenergic agonists, total beta-adrenergic receptor (beta 1 plus beta 2) density was not decreased in patients treated with enoximone or enoximone plus intravenous beta-adrenergic agonists, but was decreased by 31% (p less than 0.05) in patients given intravenous beta-adrenergic agonists alone. Additionally, patients treated with enoximone had higher myocardial beta 2-adrenergic receptor densities than respective subgroups treated without (28% higher, p less than 0.01) or with (65% higher, p less than 0.01) intravenous beta-adrenergic agonists. Finally, isoproterenol- or calcium-mediated contractile responses in isolated right ventricular preparations from 14 patients treated with enoximone were similar to values in control patients not exposed to enoximone or intravenous beta-adrenergic agonists, suggesting that enoximone-related beta-adrenergic subsensitivity or damage to the contractile apparatus does not occur.
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PMID:Low-dose enoximone in subjects awaiting cardiac transplantation. Clinical results and effects on beta-adrenergic receptors. 165 Aug 67

Changes in the beta-adrenergic receptor-G protein-adenylate cyclase complex were investigated in an experimental canine model of low-output heart failure produced by chronic rapid ventricular pacing. The contractile response occurring after exposure to the beta-adrenergic agonist dobutamine, measured as peak left ventricular + dP/dt, was decreased after 3 weeks of pacing. To further characterize the diminished functional responsiveness to beta-adrenergic receptor stimulation, beta-adrenergic receptor-adenylate cyclase coupling was investigated using membranes prepared from both control and paced animals. The density of beta-adrenergic receptors was decreased by 40% with a selective downregulation of the beta 1-subtype. The affinity of the receptor for the antagonist radioligand [125I]iodocyanopindolol remained unchanged. A defect in coupling was suggested by a decreased ability of isoproterenol, fluoride, and forskolin to stimulate adenylate cyclase in membranes prepared from failing hearts. Determination of the levels of Gi alpha (the alpha-subunit of Gi) by immunoblotting and pertussis toxin labeling revealed modest increases of approximately 30%. Furthermore, Mn2+ and purified Gs failed to stimulate adenylate cyclase in membranes prepared from failing hearts, indicating an impairment in the catalytic moiety of adenylate cyclase itself or in the ability of adenylate cyclase to couple to Gs. In contrast, complementation assay did not reveal differences in the functional activity of Gs alpha (the alpha-subunit of Gs). Taken together, these data demonstrate a selective decrease in the beta 1-subtype of adrenergic receptors and an increase in a 40-kd G1-like protein in the failing heart. Similar changes have been described in human idiopathic dilated cardiomyopathy. In addition to these changes, we identified a possible defect at the level of the catalytic subunit of adenylate cyclase.
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PMID:Beta-adrenergic receptor-G protein-adenylate cyclase complex in experimental canine congestive heart failure produced by rapid ventricular pacing. 165 3

Circulating plasma concentrations of norepinephrine, renin, angiotensin and vasopressin are increased in congestive heart failure. By increasing ventricular afterload, heart failure is further worsened, which in turn--in a vicious cycle--stimulates neurohumoral vasoconstrictor mechanisms. Furthermore, because of the compensatory but excessive stimulation of the sympathomimetic system, a down-regulation and desensitization particularly of the myocardial beta 1 receptors and depletion of myocardial catecholamine occurs in chronic heart failure. These defects may be restored toward normal by interventions that attenuate the activity of the sympathetic nervous system. A direct approach to modify the excessive vasoconstriction is to administer systemic vasodilator drugs, but despite favorable short-term effects, tolerance developed to most of these drugs during long-term treatment. One reason for the loss of effectiveness is the reflex activation of the sympathetic system, which increases vasoconstrictor hormone concentrations. Activation of the renin-angiotensin system can be modified effectively by angiotensin-converting enzyme inhibitors that have shown favorable responses in patients with chronic heart failure. Beta-blocking agents interfere with endogenous sympathetic activation and have produced beneficial effects in patients with congestive cardiomyopathy. Long-term treatment is associated with up-regulation of the number of beta receptors and an improved responsiveness to catecholamines. Owing to the negative inotropic effects of beta-blocking agents, some of the patients with severe heart failure deteriorated hemodynamically and clinically. Theoretically, it should be advantageous to have a substance that combines protection against excessive beta stimulation with a mild inotropic support to prevent cardiac decompensation. This may be achieved by a selective beta 1-partial agonist like xamoterol.
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PMID:Interrupting the adaptive changes in congestive heart failure. 167 86

Xamoterol, a new beta 1 partial agonist, has the potential to modulate cardiac response to variations in sympathetic tone in patients with heart failure. Its properties should result in beta-receptor stimulatory effects at low levels of sympathetic tone and beta-receptor protective effects at higher levels of sympathetic tone. The acute effects of intravenous (i.v.) xamoterol on hemodynamics at rest and during exercise were studied in 30 patients with mild to moderate heart failure (13 patients in New York Heart Association class II; 17 in class III) due to ischemic (n = 24) or cardiomyopathic (n = 6) heart disease. Cardiac index, stroke volume and stroke work index at rest were significantly improved after i.v. administration of xamoterol and consistent with net agonist effects. During exercise, heart rate and double product were significantly reduced (net antagonist effects), but with preservation of the expected increases in cardiac index and systolic blood pressure. These hemodynamic findings confirm the ability of xamoterol to modulate cardiac response to variations in sympathetic tone. Tachyphylaxis and arrhythmogenicity limit the chronic use of drugs with full beta-agonist properties as positive inotropes in heart failure. The patients were therefore entered into a 6-month double-blind, placebo-controlled, crossover study of chronic oral xamoterol therapy, 200 mg twice daily, and the hemodynamic responses to i.v. xamoterol were repeated at the end of the trial. No impairment in either resting or exercise effects was observed, indicative of a maintained response and absence of tachyphylaxis after chronic therapy. Furthermore, 24-hour ambulatory electrocardiographic monitoring showed no change in ventricular arrhythmias during oral treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Acute and chronic hemodynamic effects of xamoterol in mild to moderate congestive heart failure. 167 87


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