Wendy J. Coutie

Comparison of atrial natriuretic peptide, B-type natriuretic peptide, and N-terminal proatrial natriuretic peptide as indicators of left ventricular systolic dysfunction

We have directly compared atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and N-terminal pro-ANP (N-ANP) as markers of patients with left ventricular ejection fraction (LVEF) < or = 35%, as measured by radionuclide ventriculography. Venous blood samples were obtained from an unselected group of 87 patients who had been referred for assessment of ventricular function. ANP, BNP, and N-ANP were measured by radioimmunoassay using commercial kits. Receiver-operating characteristic analysis was used for the objective assessment of the diagnostic performance of each assay. There was a weak negative correlation between LVEF and plasma levels of ANP-li (r = -0.50,), BNP-li (r = -0.57), and N-ANP-li (r = -0.49) (p <0.01 for each peptide). Areas under the receiver-operating characteristic curves for BNP (0.880) and N-ANP (0.832) were not significantly different from each other, but were both significantly greater than the value for ANP (0.761): BNP versus ANP, p <0.01; and N-ANP versus ANP, p <0.05. The optimal sensitivity and specificity of each assay for the detection of patients with LVEF < or = 35% were: BNP > 4 pmol/L-sensitivity 1.0, specificity 0.58; N-ANP >200 pmol/L-sensitivity 0.95, specificity 0.35; and ANP >10 pmol/L-sensitivity 0.90, specificity 0.30. Plasma concentrations of BNP and N-ANP provide sensitive indicators of moderate to severe LV dysfunction; both peptides, are objectively superior to ANP for identifying patients with LVEF < or = 35%. These simple tests could be used to screen patients with suspected ventricular dysfunction to reduce the demand for further cardiac investigations.

Evaluation of treatment response in patients with seasonal allergic rhinitis using domiciliary nasal peak inspiratory flow

Measurement of domiciliary nasal peak inspiratory flow rate (PIFR) may have a role in the objective assessment of treatment response in seasonal allergic rhinitis (SAR).

Dietary sodium loading increases plasma brain natriuretic peptide levels in man

The effect of dietary sodium loading on plasma human brain natriuretic peptide-like immunoreactivity (hBNP-li) was examined in 11 normotensive subjects aged 20-23 years. Plasma hBNP-li increased significantly with increasing dietary sodium intake, with levels of 1.33 +/- 0.17 pmol/l on day 5 of a normal-sodium diet (24-h urinary sodium excretion of 171 +/- 16 mmol) and 2.04 +/- 0.10 pmol/l (P less than 0.05, versus normal-sodium diet) on day 5 of a high-sodium diet (24-h urinary sodium excretion 503 +/- 36 mmol). Corresponding plasma atrial natriuretic factor levels were 5.6 +/- 1.7 pmol/l and 11.0 +/- 2.0 pmol/l (P less than 0.05, versus normal-sodium diet) on the normal- and high-sodium diets, respectively. These results suggest that, in addition to atrial natriuretic factor, BNP may be a new and important natriuretic peptide which regulates sodium homeostasis in man during increased sodium intake.

A comparison of once daily fexofenadine versus the combination of montelukast plus loratadine on domiciliary nasal peak flow and symptoms in seasonal allergic rhinitis

Background The combination of montelukast (ML) and loratadine (LT) has previously been shown to be superior to either drug alone in managing seasonal allergic rhinitis (SAR), whilst fexofenadine (FEX) has been shown to be better than LT as monotherapy.

Haemodynamic and endocrine effects of type 1 angiotensin II receptor blockade in patients with hypoxaemic cor pulmonale

OBJECTIVES Angiotensin II (ANG II) is known to be a potent vasoconstrictor agent in the pulmonary circulation. Furthermore, type 1 ANG II receptor blockade with losartan attenuates acute hypoxic pulmonary vasoconstriction in normal subjects. The aim of this study was therefore to evaluate the haemodynamic and endocrine sequelae of type 1 ANG II receptor blockade in patients with hypoxaemic cor pulmonale. METHODS Nine patients with chronic obstructive pulmonary disease (COPD) age 67 +/- 3 years with pulmonary hypertension and normal left ventricular systolic function were studied on two separate occasions in a double-blind, placebo-controlled, crossover study. They were randomised to receive either 50 mg of oral losartan or matched placebo. Pulsed wave Doppler echocardiography was used to measure cardiac output (CO), mean pulmonary artery pressure (MPAP) and hence systemic vascular resistance (SVR) and total pulmonary vascular resistance (TPR). Haemodynamic measurements and venous blood samples were taken at baseline and after 2 and 4 h. RESULTS Maximal effects were observed at 4 h where losartan compared to placebo resulted in a significant reduction in both MPAP (28.6 +/- 2.0 vs 32.4 +/- 1.5 mmHg) and TPR (428 +/- 40 vs 510 +/- dyn.s.cm-5), respectively. Similarly losartan compared to placebo resulted in a significant reduction in MAP (87 +/- 4.5 vs 93 +/- 3.2 mmHg) and SVR (1293 +/- 94 vs 1462 +/- 112 dyn.s.cm-5), and significantly increased CO (5.58 +/- 0.43 vs 5.31 +/- 0.42 l/min). In addition, plasma aldosterone was significantly lower after treatment with losartan compared to placebo: 76 +/- 23 vs 164 +/- 43 pg/ml respectively. CONCLUSIONS Thus, selective type 1 ANG II receptor blockade appears to have beneficial pulmonary and endocrine effects, suggesting a possible therapeutic role in the management of hypoxaemic cor pulmonale.

Evaluation of the metabolic responses to inhaled salbutamol in the measurement of beta2-adrenoceptor blockade

SummaryThe aim of the present study was to evaluate whether metabolic responses to inhaled salbutamol may be used to measure the cardioselectivity of beta-adrenoceptor antagonists. We therefore studied the effects of oral doses of atenolol 50 mg, 100 mg, 200 mg (A50, A100, A200), propranolol 40 mg (P40), and placebo (Pl) on the hypokalaemic (K) and hyperglycaemic (Glu) responses to inhaled salbutamol in five healthy subjects.Increasing doses of atenolol were associated with a progressive attenuation of ΔK compared with placebo: −0.72 mmol·l−1 (Pl) vs −0.20 mmol·l−1 (A200). However, ΔK with A200 was significantly different from the response with P40: +0.12 mmol·l−1. There were partial reductions in the hyperglycaemic response with the beta-adrenoceptor antagonists, although this was only significant (compared with Pl) for P40: ΔGlu 1.92 mmol·l−1 (Pl) vs 0.76 mmol·l−1 (P40).These results show that beta2-adrenoceptor blockade by atenolol is a dose-dependent phenomenon, which may be measured by the attenuation of salbutamol-induced hypokalaemia. However, beta2-adrenoceptor blockade by atenolol 200 mg was less than that by propranolol 40 mg. The glucose response to salbutamol was only partially blocked by propranolol and may therefore not be suitable to assess beta2-adrenoceptor antagonism.

The effect of intravenous saline loading on plasma levels of brain natriuretic peptide in man.

Objective: Recent evidence suggests the presence of a dual natriuretic peptide system consisting of atrial natriuretic factor (ANF) from the atrium and brain natriuretic peptide (BNP) from the ventricle. Discrete roles have been postulated for these two natriuretic peptides in the control of circulatory homeostasis. We have therefore compared the release of ANF and BNP in response to an acute saline load to explore a differential pattern of release for the two natriuretic peptides in man. Design: The effects of an acute saline infusion on plasma ANF and BNP concentrations were studied in 10 normal male volunteers. Methods: Subjects were studied on two study days in the semirecumbent position. An acute intravenous saline infusion (250ml/min) of 18 ml/kg isotonic sodium chloride-potassium chloride solution was administered on one of the two study days. No infusion was administered on the other day as a control. Results: Plasma ANF concentrations increased significantly (P<0.01) with saline loading without any detectable changes in plasma BNP concentrations up to 60 min following infusion. Heart rate and systolic and diastolic blood pressure were unchanged after saline loading. Conclusions: We have shown that an acute intravenous saline load causes an increase in plasma ANF concentrations with no detectable increase in plasma BNP at least up to 60 min after the acute saline load in man. These results support the view that the release of ANF and BNP may be regulated differently, especially with regard to the time required for the acute release of each peptide.

C-type natriuretic peptide levels in cor pulmonale and in congestive heart failure.

BACKGROUND--C-type natriuretic peptide (CNP) is a recent addition to the family of natriuretic peptides which includes atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). Whilst the levels of ANP and BNP are increased in conditions such as congestive heart failure and cor pulmonale, abnormal levels of CNP in these conditions have not been reported. METHODS--Plasma levels of CNP were measured by specific radioimmunoassay in 12 young normal controls, 12 elderly normal controls, 12 patients with NYHA grade III-IV congestive heart failure, and in 16 patients with hypoxaemic cor pulmonale. RESULTS--Mean (SE) plasma levels of CNP were similar in young normal controls (0.46(0.03) pmol/l), elderly normal controls (0.43(0.05) pmol/l), and in patients with congestive heart failure (0.33(0.2) pmol/l). In patients with cor pulmonale, however, plasma levels of CNP were raised (1.39(0.27) pmol/l) 3.2-fold compared with age-matched controls. CONCLUSIONS--In cor pulmonale the increased plasma levels of CNP were not as great as the previously observed increases in levels of ANP (5.6-fold) or BNP (18.5-fold) in comparable patients. CNP may therefore be less important than ANP or BNP as a circulating counter-regulatory peptide in conditions of overactivity of the renin angiotensin system.

Plasma arginine vasopressin, atrial natriuretic peptide and brain natriuretic peptide responses to long-term field training in the heat: effects of fluid ingestion and acclimatization

Abstract The maintenance of blood volume during exercise, especially in a hot environment, is of major importance for continued performance. In order to investigate the relationships between exercise, type and amount of fluid intake and the degree of acclimatization to heat stress and on responses of arginine vasopressin (AVP), atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), we studied 24 soldiers during and after jogging/walking exercise both before and after acclimatization to field training at [mean (SE)] 40 (0.7) °C and 32 (3)% relative humidity. The running exercise was carried out under three conditions, i.e., (1) without any fluid intake, (2) with intake of water or (3) with intake of a dextrose/electrolyte solution. Venous blood samples were drawn before exercise, at the end of exercise and at 15 min and 60 min afterwards. Acclimatization resulted in significant losses of body mass, total body water, plasma volume, ANP and increases in plasma osmolality, packed cell volume and AVP at rest but without any significant changes in BNP. During exercise with no fluid intake, there was a significant rise in plasma osmolality, Na+ and AVP, but no significant alterations in plasma ANP and BNP were observed. When subjects ingested water or dextrose/electrolyte solution during exercise, ANP rose by 234% and 431% respectively and BNP rose by 398% and 583% respectively without any significant increase in AVP. The results suggest that, during acclimatization, the subjects became slightly dehydrated. Alterations in response to changes in body water status appear to be greater for AVP than ANP or BNP at rest. During exercise in the heat ANP and BNP may play complementary roles.

Evidence in humans for a postsynaptic interaction between noradrenaline and angiotensin II with regard to systolic but not diastolic blood pressure.

Much animal evidence exists to suggest that there is an interaction between noradrenaline (NA) and angiotensin II (AII). We have now sought evidence for a postsynaptic AII/NA interaction. Ten normotensive volunteers were infused with dextrose/saline, All/saline, dextrose/NA or AII/NA in a randomized single-blind fashion. The respective increases in systolic blood pressure (SBP) were -4 +/- 6, -2 +/- 9, 4 +/- 6 and 14 +/- 16 mmHg at comparative time intervals while the corresponding increases in diastolic blood pressure (DBP) were 2 +/- 4, 6 +/- 7, 9 +/- 6 and 14 +/- 8 mmHg. ANOVA confirmed that AII and NA had a synergistic interaction (P less than 0.05) in elevating SBP while there was merely an additive effect in elevating DBP. Plasma NA and AII levels were unchanged by the coincidental presence of AII and NA, respectively, which excludes a generalized pharmacokinetic interaction between AII and NA. This study provides evidence for a postsynaptic AII/NA interaction with regard to SBP but not DBP although the precise location of this interaction remains uncertain. Therefore, in considering the pathogenesis of SBP abnormalities, concomitant measurements of both NA and AII may be important.