Expression and distribution of renal vacuolar proton-translocating adenosine triphosphatase in response to chronic acid and alkali loads in the rat.

Renal hydrogen ion excretion increases with chronic acid loads and decreases with alkali loads. We examined the mechanism of adaptation by analyzing vacuolar proton-translocating adenosine triphosphatase (H+ ATPase) 31-kD subunit protein and mRNA levels, and immunocytochemical distribution in kidneys from rats subjected to acid or alkali loads for 1, 3, 5, 7, and 14 d. Acid- and alkali-loaded rats exhibited adaptive responses in acid excretion, but showed no significant changes in H+ ATPase protein or mRNA levels in either cortex or medulla. In contrast, there were profound adaptive changes in the immunocytochemical distribution of H+ ATPase in collecting duct intercalated cells. In the medulla, H+ ATPase staining in acid-loaded rats shifted from cytoplasmic vesicles to plasma membrane, whereas in alkali-loaded rats, cytoplasmic vesicle staining was enhanced, and staining of plasma membrane disappeared. In the cortical collecting tubule, acid loading increased the number of intercalated cells showing enhanced apical H+ ATPase staining and decreased the number of cells with basolateral or poorly polarized apical staining. The results indicate that both medulla and cortex participate in the adaptive response to acid and alkali loading by changing the steady-state distribution of H+ ATPase, employing mechanisms that do not necessitate postulating interconversion of intercalated cells with opposing polarities.

[Heart rate as a cardiovascular risk factor: potential clinical benefit with ivabradine]. / Fréquence cardiaque comme facteur de risque cardiovasculaire: potentiel de l'ivabradine.

Elevated resting heart rate is an independent cardiovascular risk factor and rate reduction is beneficial. It is not known whether reduction of heart rate per se can improve outcome. Studies of beta-blockers in post-myocardial infarction patients suggest that this may be the case, but beta-blockers, may be poorly tolerated or contraindicated. Similarly, heart rate lowering calcium antagonists are associated with modest event-rate reduction only in selected patients. The new selective inhibitor of the sinus node If current, ivabradine, looks promising in terms of reducing myocardial ischaemia. Its mode of action, the exclusive reduction of heart rate through selective inhibition of the sinus node If current, provides comparable efficacy to existing treatments. Ivabradine is licensed in Europe for use in stable angina.

Diuretics for heart failure.

BACKGROUND: Chronic heart failure is a major cause of morbidity and mortality world-wide. Diuretics are regarded as the first-line treatment for patients with congestive heart failure since they provide symptomatic relief. The effects of diuretics on disease progression and survival remain unclear. OBJECTIVES: To assess the harms and benefits of diuretics for chronic heart failure SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (Issue 2 2004), MEDLINE 1966-2004, EMBASE 1980-2004 and HERDIN database. We hand searched pertinent journals and reference lists of papers were inspected. We also contacted manufacturers and researchers in the field. SELECTION CRITERIA: Only double-blinded randomised controlled trials of diuretic therapy comparing one diuretic with placebo, or one diuretic with another active agent (e.g. ACE inhibitors, digoxin) in patients with chronic heart failure were eligible for inclusion. DATA COLLECTION AND ANALYSIS: Two reviewers independently abstracted the data and assessed the eligibility and methodological quality of each trial. Extracted data were entered into the Review Manager 4.2 computer software, and analysed by determining the odds ratio for dichotomous data, and difference in means for continuous data, of the treated group compared with controls. The likelihood of heterogeneity of the study population was assessed by the Chi-square test. If there was no evidence of statistical heterogeneity and pooling of results was clinically appropriate, a combined estimate was obtained using the fixed-effects model. MAIN RESULTS: We included 14 trials (525 participants), 7 were placebo-controlled, and 7 compared diuretics against other agents such as ACE inhibitors or digoxin. We analysed the data for mortality and for worsening heart failure. Mortality data were available in 3 of the placebo-controlled trials (202 participants). Mortality was lower for participants treated with diuretics than for placebo, odds ratio (OR) for death 0.24, 95% confidence interval (CI) 0.07 to 0.83; P = 0.02. Admission for worsening heart failure was reduced in those taking diuretics in two trials (169 participants), OR 0.07 (95% CI 0.01 to 0.52; P = 0.01). In four trials comparing diuretics to active control (91 participants), diuretics improved exercise capacity in participants with CHF, difference in means WMD 0.72 , 95% CI 0.40 to 1.04; P < 0.0001. AUTHORS' CONCLUSIONS: The available data from several small trials show that in patients with chronic heart failure, conventional diuretics appear to reduce the risk of death and worsening heart failure compared to placebo. Compared to active control, diuretics appear to improve exercise capacity.

Potassium channel openers in myocardial ischaemia: therapeutic potential of nicorandil.

Potassium channel openers or agonists represent a novel new class of compounds in the treatment of a range of cardiovascular disorders, particularly angina pectoris and hypertension. Nicorandil is the only clinically available potassium channel opener with antianginal effects, and with comparable efficacy and tolerability to existing antianginal therapy. It confers benefits through a dual action: opening the mitochondrial KATP channels leading to preconditioning of the myocardium and a nitrate-like effect. Myocardial preconditioning is important in reducing infarct size, severity of stunning and cardiac arrhythmias. These effects make nicorandil a unique antianginal compound that reduces both pre- and after-load and improves coronary blood flow. Comparative and noncomparative studies support the use of nicorandil as monotherapy or in combination with other antianginal therapy for stable angina pectoris. However, large studies are required to confirm its role in the treatment of acute coronary syndromes despite the favourable results from small studies.

Clinical depression is common and significantly associated with reduced survival in patients with non-ischaemic heart failure.

Several studies have shown that depression is an important predictor of morbidity and mortality in patients with ischaemic heart failure. We have investigated whether clinically recognised depression is linked to mortality in patients with non-ischaemic heart failure due to dilated cardiomyopathy (DCM) in the Royal Brompton Hospital (RBH), a tertiary cardiac centre located in London, UK. We retrospectively examined a cohort of 396 consecutive adult patients with DCM who satisfied our inclusion and exclusion criteria identified from an echocardiographic database and the hospital medical records. Mean age was 53+/-15 years. In all, 83 patients (21%) were clinically depressed, the majority of which (60%) were taking antidepressant therapy. After a follow-up period of 48 months, 83 (21%) patients died, 15 (4%) underwent cardiac transplantation and 130 (33%) were readmitted; 29 (35%) of the deaths and 40 (31%) of the readmissions were among clinically depressed patients. After 5 years, clinically depressed patients had significantly higher mortality and readmission rates than non-depressed; 36 vs. 16% (hazards ratio for death, 3.0; 95% CI, 1.4-6.4; P=0.004), and 87 vs. 74% (hazards ratio for readmission, 0.25; 95% CI, 0.07-0.90; P=0.03), respectively. The risk of depression was greatly increased in the presence of other recognised adverse clinical variables at baseline. Depression increases the risk of death and readmission in patients with heart failure secondary to non-ischaemic DCM. The risk associated with depression appears to be greatest among patients with milder disease, those with a shorter duration of symptoms and those demonstrating a lower systolic or diastolic blood pressure, renal impairment, or a restrictive left ventricular physiology on echocardiography. Interventions targeted at reducing depression warrant further study as a possible way to improve quality of life and/or outcome in patients with heart failure.

Maturational changes in steroidogenesis in the inner and outer zones of the guinea pig adrenal cortex.

Studies were done to determine the effects of age on steroidogenesis in the inner (zona reticularis) and outer (zona fasciculata plus glomerulosa) zones of the guinea pig adrenal cortex. In 35-day-old animals, cortisol production by adrenal outer zone cells was approximately twice as great as that by inner zone cells. With aging, cortisol secretion by inner zone cells decreased to very low levels, but there was no detectable change in the capacity for cortisol production by the outer zone. However, the outer zone comprised a progressively decreasing fraction of the total adrenal mass in older animals. To determine the basis for the decline in cortisol production by inner zone cells with aging, the activities of several steroidogenic enzymes were determined. Microsomal 21-hydroxylase activity was greater in the inner than outer zone but was not significantly affected by age. By contrast, 17 alpha-hydroxylase activity was greater in the outer zone at all ages, and decreased with aging in the inner but not the outer zone. Mitochondrial cholesterol sidechain cleavage and 11 beta-hydroxylase activities were also higher in the outer than inner zone and declined in the inner zone only in older animals. The decrease in inner zone cholesterol sidechain cleavage activity with aging was proportionately greater than the age-dependent changes in other enzyme activities. The results indicate that the effects of aging on steroidogenesis are both zone- and enzyme-specific. The overall decline in cortisol secretion by the guinea pig adrenal cortex with aging is attributable to both a decrease in cortisol production by the cells of the zone reticularis and a disproportionate increase in the mass of the gland comprised by this zone. The decrease in cortisol secretion correlates closely with a decline in cholesterol sidechain cleavage activity in the zona reticularis, and may be causally related.

Early continuous ST segment monitoring in unstable angina: prognostic value additional to the clinical characteristics and the admission electrocardiogram.

BACKGROUND AND OBJECTIVE: In unstable angina, clinical characteristics, resting electrocardiography, and early continuous ST segment monitoring have been individually reported to identify subgroups at increased risk of adverse outcome. It is not known, however, whether continuous ST monitoring provides additional prognostic information in such a setting. DESIGN: Observational study of 212 patients with unstable angina without evidence of acute myocardial infarction admitted to district general hospitals, who had participated in a randomised study comparing heparin and aspirin treatment versus aspirin alone. METHODS: Clinical variables and a 12 lead electrocardiogram (ECG) were recorded at admission, and treatment was standardised to include aspirin, atenolol, diltiazem, and intravenous glyceryl trinitrate, in addition to intravenous heparin (randomised treatment). Continuous ST segment monitoring was performed for 48 h and all inhospital adverse events were recorded. RESULTS: The admission ECG was normal in 61 patients (29%), showed ST depression in 59 (28%) (17 > or = 0.1 mV), and T wave changes in a further 69 (33%). The remaining 23 had Q waves (18), right bundle branch block (four), or ST elevation (one). During 8963 h of continuous ST segment monitoring (mean 42.3 h/patient), 132 episodes of transient myocardial ischaemia (104 silent) were recorded in 32 patients (15%). Forty patients (19%) had an adverse event (cardiac deaths (n = 3), non-fatal myocardial infarction (n = 6) and, emergency revascularisation (n = 31)). Both admission ECG ST depression (P = 0.02), and transient ischaemia (P < 0.001) predicted an increased risk of non-fatal myocardial infarction or death, while no patients with a normal ECG died or had a myocardial infarction. Adverse outcome was predicted by admission ECG ST depression (regardless of severity) (odds ratio (OR) 3.41) (P < 0.001), and maintenance beta blocker treatment (OR 2.95) (P < 0.01). A normal ECG predicted a favourable outcome (OR 0.38) (P = 0.04), while T wave or other ECG changes were not predictive of outcome. Transient ischaemia was the strongest predictor of adverse prognosis (OR 4.61) (P < 0.001), retaining independent predictive value in multivariate analysis (OR 2.94) (P = 0.03), as did maintenance beta blocker treatment (OR 2.85) (P = 0.01) and admission ECG ST depression, which showed a trend towards independent predictive value (OR 2.11) (P = 0.076). CONCLUSIONS: Patients with unstable angina and a normal admission ECG have a good prognosis, while ST segment depression predicts an adverse outcome. Transient myocardial ischaemia detected by continuous ST segment monitoring in such patients receiving optimal medical treatment provides prognostic information additional to that gleaned from the clinical characteristics or the admission ECG.

Adrenal activation of carbon tetrachloride: role of microsomal P450 isozymes.

Previous investigations demonstrated that carbon tetrachloride (CCl4) was activated by adrenal microsomes, resulting in various functional changes and ultimately in necrosis of the zona reticularis of the gland. Experiments were done to identify the adrenal P450 isozyme(s) involved in the bioactivation of CCl4. Incubation of microsomes from the zona reticularis (ZR) of the guinea pig adrenal cortex with CCl4 plus NADPH caused initiation of lipid peroxidation, covalent binding of CCl4-derived radioactivity to protein, and degradation of cytochrome(s) P450. Preincubation of the microsomal preparations with inhibitory antibodies to P450(17 alpha) or P450C21 decreased the corresponding enzyme activities (17 alpha-hydroxylation and 21-hydroxylation), but did not affect the activation of CCl4. 1-Aminobenzotriazole (ABT), a suicide inhibitor of some P450 isozymes, decreased the enzyme activities catalysed by an adrenal 52,000 Da (52 kDa) isozyme, but had no effect on the function of P450(17 alpha) or P450C21. However, ABT completely inhibited the CCl4-induced LP and covalent binding in adrenal microsomes. The results indicate that adrenal CCl4 activation is catalysed by the 52 kDa P450 isozyme and not by the steroid hydroxylases. Localization of the 52 kDa isozyme to the ZR probably accounts for the selective necrosis of this region of the gland by CCl4.

Ambulatory blood pressure monitoring and circadian variation of cardiovascular disease; clinical and research applications.

Ambulatory blood pressure monitoring is an evolving technology. It has an established role in the diagnosis of hypertension, the clinical management of selected patients, and in the evaluation of new medication. From continuous recording much has been learned about the circadian nature of blood pressure and heart rate. Future research holds promise for a greater understanding of the mechanisms and treatment of cardiovascular disease. The purpose of this short review is to describe the development of ambulatory blood pressure monitoring, and outline some of its important contributions to date; and also to explore the research potential and clinical utility of advanced intravascular monitoring techniques, such as the continuous recording of pulmonary artery pressure in ambulant patients.

Current evidence supporting the role of diuretics in heart failure: a meta analysis of randomised controlled trials.

OBJECTIVE: To summarise the current evidence from randomised controlled trials for diuretics in patients with congestive heart failure (CHF). DATA SOURCES: English-language randomised controlled trials and review papers referenced in Medline, Embase between 1966 and 1999. General literature review of pertinent journals was carried out and reference lists of papers were inspected. STUDY DESIGN: Meta-analysis of randomised controlled trials of diuretic therapy in patients with CHF. STUDY SELECTION: Studies were included if they were randomised comparisons of loop or thiazide diuretics and control, or one diuretic and another active agent (e.g. ACE inhibitors, ibopamine and digoxin). DATA ABSTRACTION: Using a standardised protocol, two reviewers independently abstracted the data and assessed the methodological quality of each paper. DATA SYNTHESIS: The odds ratio (OR) of treated group compared with control was estimated for each end-point outcome and plotted against each other using the fixed-effects model. THE MAIN OUTCOME MEASURES: The primary outcomes of our analysis were effects of diuretics on mortality and morbidity. RESULTS: Eighteen trials met our criteria and were eligible for analysis, involving 928 patients. Eight trials were placebo-controlled. We analysed the data for mortality and for worsening heart failure. A further ten trials compared diuretics against other agents such as ACE inhibitors, ibopamine, and digoxin. Mortality data were available in three of the placebo-controlled trials (n=221); the mortality rate was lower for patients treated with diuretics than for control [the odds ratio for death, 0.25; 95% confidence intervals (CI), 0.07-0.84; P=0.03]. Admissions for worsening heart failure in the four small trials (n=448) showed an odds ratio of 0.31 (95% CI 0.15-0.62; P=0.001). In six studies of diuretics compared to active control, diuretics significantly improved exercise capacity in patients with CHF [OR: 0.37; CI: 0.10-0.64, P=0.007]. CONCLUSION: Compared to active control, diuretics appear to reduce the risk of worsening disease and improve exercise capacity. The available data from small studies show that in CHF conventional diuretics reduce the risk of death and worsening heart failure compared to placebo.

Circadian patterns of myocardial ischaemia and the effects of antianginal drugs.

Chronopathology of cardiovascular disease is now well documented. Silent myocardial ischaemia involves the same pathophysiological changes as conventional ischaemia. Early morning peaks in angina and myocardial ischaemia call for adequate timing of medication. beta-blockers abolish the morning peak, and aspirin reduces morning infarctions. The effects of other antianginals on these phenomena are presently unknown.