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. OBJECTIVES: We wished to compare ML + LT vs. FEX alone for effects on daily measurements (am/pm) of peak inspiratory flow (PIF) and symptoms. METHODS: Thirty-seven patients with SAR (skin prick positive to grass pollen) were randomised into a single-blind, double-dummy placebo (PL)-controlled cross-over study during the grass pollen season, comparing 2 weeks of once daily treatment with (a) 120mg FEX or (b) 10mg ML + 10mg LT. There was a 7-10 day placebo run-in and washout prior to each randomised treatment. The average of am/pm PIF (the primary outcome variable) was analysed. Patients recorded their symptom scores (from 0 to 3) twice daily, for nasal blockage, discharge, itching and sneezing with; total eye symptoms, ocular cromoglycate use, and daily activity. The total nasal symptom score was calculated as a composite (out of 24). RESULTS: There were no significant differences between baselines after the run-in and washout placebos for any variables. There were significant (P < 0.05, Bonferroni) improvements in all symptoms and PIF compared to pooled placebo with both treatments for all end-points, but no differences between the two treatment regimes (as means and within-treatment 95% confidence intervals): PIF: PL 102 (98-107), FEX 111 (107-116), ML+LT 113 (109-118); total nasal symptoms: PL 7.4 (6.7-2.0), FEX 5.0 (4.3-5.7), ML + LT 4.0 (3.3-4.7). CONCLUSIONS: Once daily FEX as monotherapy was equally effective as the combination of once daily ML + LT in improving nasal peak flow and controlling symptoms in SAR. Further studies are indicated to assess whether ML confers additional benefits to FEX in SAR.

Beta2 adrenoceptor promoter polymorphisms: extended haplotypes and functional effects in peripheral blood mononuclear cells.

BACKGROUND: The beta2 adrenoceptor and its 5' untranslated region contain a number of genetic variants. The aim of this study was to investigate the potential for genetic variation at this locus to influence the expression of beta2 adrenoceptors on circulating peripheral blood mononuclear cells (PBMCs). METHODS: Genotype was determined in 96 individuals with asthma for four polymorphisms at the beta2 adrenoceptor locus. Beta2 adrenoceptor binding and cyclic AMP responses to isoprenaline in PBMCs were determined and the relationship between genotype/haplotype and beta2 adrenoceptor expression and response to isoprenaline examined. RESULTS: Beta2 adrenoceptor promoter polymorphisms were found to be common in white subjects. Strong linkage disequilibrium exists across this locus, resulting in the occurrence of several common haplotypes. No single polymorphism or haplotype was correlated with the level of beta2 adrenoceptor expression or cyclic AMP responses to isoprenaline in vitro. CONCLUSION: Beta2 adrenoceptor polymorphisms, when considered in isolation or by extended haplotypes, do not determine the basal level of expression or coupling of beta2 adrenoceptors in PBMCs from asthmatic subjects.

Effects of topical corticosteroid and combined mediator blockade on domiciliary and laboratory measurements of nasal function in seasonal allergic rhinitis.

BACKGROUND: Both domiciliary and laboratory measures of nasal function have been used to evaluate treatment response in allergic airways disease; however, these measures have not been compared. OBJECTIVE: To determine the relationship of domiciliary measures (daily symptoms, peak inspiratory nasal flow, and nasal oral index) and laboratory measures (rhinomanometry, acoustic rhinometry) in assessing treatment response with topical steroids and specific inflammatory mediator blockage. METHODS: Twenty-one patients with seasonal allergic rhinitis and asthma were enrolled into a single-blind, placebo-controlled, crossover study comparing 2 weeks of 1) 400 microg inhaled plus 200 microg intranasal budesonide once daily and 2) 10 mg montelukast plus 10 mg cetirizine once daily. Before each treatment, patients received 7 to 10 days of placebo period. Laboratory measurements were made of nasal resistance by posterior rhinomanometry, and nasal volume between 0 and 5 cm by acoustic rhinometry after both placebo and active treatment periods. Daily domiciliary recordings were made of allergic rhinitis nasal symptoms scores and peak nasal and oral inspiratory flow rate (enabling the calculation of a nasal/oral index) throughout the study. RESULTS: There were significant (P < 0.05) improvements for all allergic rhinitis symptoms with both therapies, after factoring for pollen count. Spearman's rank correlation for comparison among nasal symptoms and the objective responses were: nasal inspiratory flow rate (R = -0.50, P = 0.02); nasal/oral index (R = -0.55 P = 0.01); rhinomanometry (R = 0.24, P = 0.30); and acoustic rhinometry (R = -0.21, P = 0.36). CONCLUSIONS: Both treatments were effective in managing allergic rhinitis symptoms, and patients' symptoms were more closely associated with domiciliary measurements of nasal flow than laboratory measurements of nasal function.

Relative lung delivery of fluticasone propionate via large volume spacer or nebuliser in healthy volunteers.

OBJECTIVES: High-dose nebulised fluticasone propionate (FP) has been advocated for use in patients with severe persistent asthma. As there is complete first-pass inactivation of FP for the swallowed fraction, systemic absorption is due solely to its lung bioavailability. We wished to compare the relative lung delivery of FP, using adrenal suppression as a surrogate for the respirable dose, when administered via large volume spacer (FP-spacer) or nebuliser (FP-neb) in healthy adults. METHODS: Fourteen healthy subjects, mean (SEM) age 29.4 +/- 2.6 years, were studied in a placebo-controlled, randomised study with three-way crossover design. Single nominal 2-mg doses of the following were given at 1700 hours in randomised sequence: a. FP-spacer: fluticasone pressurised metered dose inhaler (as Flixotide 250 microg ex-valve per actuation), eight puffs via a primed Volumatic 750-ml spacer. b. FP-neb: (as Flixotide Nebule 2 mg/2 ml) via Pari LC Plus nebuliser. c. Placebo nebuliser. Following each dose, measurements were made of corrected 0800-hours urinary cortisol/creatinine ratio (the primary outcome variable) and 0800-hours plasma cortisol. RESULTS: Significant (P<0.05) suppression of both endpoints occurred only with FP-spacer, FP-neb being statistically no different from placebo. Geometric mean fold differences between FP-spacer and placebo were 9.8-fold [95% confidence interval (CI) 3.4, 28.8] for urinary cortisol/creatinine and 4.1-fold (95% CI 2.2, 7.5) for plasma cortisol. Comparing FP-spacer with FP-neb, these differences were 6.8-fold (95% CI 2.3, 20.0) for urinary cortisol/creatinine and 3.3-fold (95% CI 1.8, 6.0) for plasma cortisol. CONCLUSION: For a 2-mg labelled nominal dose of fluticasone, the spacer produced about a sevenfold higher relative lung dose than the nebuliser. This suggests that a very little of the labelled nebulised dose is respirable. Other factors such as patient preference, cost and compliance will determine the inhaler device that is chosen.

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

BACKGROUND: 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). OBJECTIVE: We wished to evaluate the relationship between domiciliary measurement of nasal PIFR and a variety of symptoms associated with rhinitis. METHODS: Thirty-eight nonasthmatic patients, mean age (SEM) 30 years (1.4), with symptomatic SAR were evaluated in a placebo-controlled, single-blind, double-dummy, three way parallel group study. Patients received oral cetirizine 10 mg once daily and were randomized to receive, in addition, either: (i) intranasal mometasone furoate 200 microgram (n = 14); (ii) oral montelukast 10 mg (n = 11); or (iii) placebo (n = 13). All treatments were given once daily for 4 weeks and were preceded by a 1 week placebo period. Domiciliary diary cards were used to record morning (am) and evening (pm) domiciliary nasal PIFR and symptom (nasal, eye, throat) scores and impact on daily activity. A total daily symptom score was then calculated from the sum of these separate symptom scores. RESULTS: Baseline values for symptom scores and PIFR after placebo run-in were not significantly different when comparing the three groups. After 4 weeks of active treatment, there were significant (P < 0.05) improvements in nasal symptoms, total daily symptoms and PIFR with all treatments, with there being no significant confounding effect of pollen count, when analysed as a covariate. There were significant (P < 0.01) correlations for nasal symptom scores vs PIFRam (r = - 0.51) and PIFRpm (r = - 0.56), and similarly for daily activity vs PIFRam (r = - 0.42) and PIFRpm (r = - 0.48). CONCLUSIONS: These results suggest that domiciliary measurements of nasal peak flow correlate significantly with symptoms of seasonal allergic rhinitis and may therefore be a potentially useful objective short-term marker of treatment response.

The effect of nitric oxide inhibition on the renin response to frusemide, in man.

AIMS: We wished to see if renin release in man was inhibited by nitric oxide blockade, suggesting a role for nitric oxide in renin release. Evidence from animal studies has shown variable effects on renin release depending on the model and stimulus used. METHODS: Ten normal male volunteers, received either L-NMMA as a front loaded infusion (4 mg kg-1 bolus, with 4 mg kg-1 infusion), or placebo, followed by an intravenous bolus of 5 mg frusemide to stimulate renin. To investigate whether any alteration in renin release was due to the pressor effect of the L-NMMA, the experiment was repeated using an equipressor dose of phenylephrine (0.5 microg kg-1 min-1 ). RESULTS: L-NMMA caused the expected increase in mean arterial pressure (96+/-2.6 vs 89+/-3.3 mmHg P<0.05 [mean+/-s.e.mean]), and a reduction in heart rate (59+/-3.6 vs 67+/-2.5 beats min-1 P<0.05). L-NMMA completely blocked the renin rise following the bolus of frusemide (1.18+/-0.196 vs 1.96+/-0.333 ng ml-1 h-1 P<0.01). Phenylephrine 0.5 microg kg-1 min-1 produced very similar haemodynamic effects to L-NMMA, and also suppressed the renin response to frusemide (1.43+/-0.290 vs 2.67+/-0.342 ng ml-1 h-1 P<0. 01). CONCLUSIONS: In man, the renin inhibition seen with NO synthesis inhibition is similar to that seen with a standard pressor stimulus, hence inhibition of renin in man by L-NMMA, may be due to both direct effects on macula densa cells and indirect haemodynamic effects.

Evaluation of the effect of a large volume spacer on the systemic bioactivity of fluticasone propionate metered-dose inhaler.

BACKGROUND: Inhaled corticosteroids such as fluticasone propionate (FP) have dose-related systemic effects, including adrenal suppression. We have therefore investigated the effect of adding a large volume spacer on the systemic bioactivity of FP given via a pressurized metered-dose inhaler (pMDI). METHODS: Fourteen healthy volunteers (mean age, 29.9 years old) were studied using an open, randomized, placebo-controlled, three-way crossover design. Single doses of the following were given at 5:00 PM in a randomized sequence: (1) eight puffs of FP by pMDI, 1.76 mg (250 microg ex-valve, 220 microg ex-actuator); (2) eight puffs of FP by pMDI, 250 microg, with 750-mL spacer (Volumatic; Allen & Hanburys; Uxbridge, UK); and (3) eight puffs of placebo by pMDI. Measurements were made after each dose, including overnight and early morning urinary cortisol/creatinine ratios and 8:00 AM serum cortisol. RESULTS: Significant (p < 0.05) suppression of all three end points occurred with each active treatment compared to treatment with placebo. Furthermore, significant (p < 0.05) additional suppression occurred when comparing FP by pMDI alone to FP by pMDI with spacer. Geometric mean fold differences (95% confidence interval for fold difference) between FP by pMDI alone and FP by pMDI with spacer were 1.94-fold (1.00-3.78) for overnight urinary cortisol/creatinine ratio and 1.98-fold (1.26-3.10) for 8:00 AM serum cortisol. This was mirrored by a twofold rise in the number of values for uncorrected overnight urinary cortisol < 10 nmol/10 h: placebo treatment (none of 14 subjects); FP by pMDI (6 of 14 subjects; 43%); and FP by pMDI with spacer (12 of 14 subjects; 86%). CONCLUSIONS: The use of a large volume spacer with FP by pMDI results in a twofold increase in the systemic bioavailability as assessed by sensitive measures of adrenal suppression. This, in turn, reflects a twofold improvement in respirable dose delivery with the spacer device.

Evaluation of the buccal component of systemic absorption with inhaled fluticasone propionate.

BACKGROUND: Inhaled corticosteroids have dose related systemic effects determined by oral (swallowed or oropharyngeal absorption) and lung bioavailability. A study was undertaken to evaluate the significance of oropharyngeal absorption for fluticasone propionate. METHODS: Sixteen healthy volunteers of mean age 29.3 years were studied using an open randomised, placebo controlled, four way crossover design. Treatments were: (a) fluticasone metered dose inhaler (pMDI) 250 microg, 8 puffs; (b) fluticasone pMDI 250 microg, 8 puffs + mouth rinsing/gargling (water); (c) fluticasone pMDI 250 microg, 8 puffs + mouth rinsing/gargling (charcoal); and (d) placebo pMDI, 8 puffs + mouth rinsing/gargling (water). Overnight (ONUC) and early morning (EMUC) urinary cortisol/creatinine ratios and 8 am serum cortisol (SC) levels were measured. RESULTS: Significant (p<0. 05) suppression of ONUC, EMUC, and SC occurred with each active treatment compared with placebo. The mean values (95% CI for difference from placebo) were: (a) ONUC (nmol/mmol): fluticasone (2. 8, 95% CI 3.6 to 7.9), fluticasone + water (3.1, 95% CI 3.3 to 7.7), fluticasone + charcoal (2.3, 95% CI 4.1 to 8.5); placebo (8.6); (b) EMUC (nmol/mmol): fluticasone (5.6, 95% CI 8.4 to 24.5), fluticasone + water (7.6, 95% CI 6.6 to 22.4); fluticasone + charcoal (5.6, 95% CI 8.7 to 24.5); placebo (22.1). There were no significant differences between active treatments. The numbers of subjects with an overnight urinary cortisol of <20 nmol/10 hours were 0 (placebo), 11 (fluticasone), 12 (fluticasone + water), and 13 (fluticasone + charcoal). CONCLUSIONS: Oropharyngeal absorption of fluticasone does not significantly contribute to its overall systemic bioactivity as assessed by sensitive measures of adrenal suppression. In view of almost complete hepatic first pass inactivation with fluticasone, there is no rationale to employ mouth rinsing to reduce its systemic effects although it may be of value for reducing oral candidiasis.

Effects of genetic polymorphism on ex vivo and in vivo function of beta2-adrenoceptors in asthmatic patients.

BACKGROUND: Genetic polymorphism determines agonist-induced down-regulation and desensitization of beta2-adrenoceptors. OBJECTIVES: The aim of the present study was to investigate the effects of genetic polymorphism on ex vivo (lymphocytes) and in vivo (bronchoprotection) function of beta2-adrenoceptors in asthmatic patients, having been washed out of previous beta2-agonist exposure. METHODS: Sixty patients with stable mild-to-moderate asthma were evaluated, with a post hoc analysis of genotype performed at end of study. Having withheld treatment with long-acting beta2-agonists for > or = 48 h and short-acting beta2-agonists for > or = 12 h, measurements of lymphocyte beta2-adrenoceptors were made for binding density, binding affinity, basal cyclic adenosine monophosphate (cAMP), and maximal cAMP response to isoproterenol (Emax). In addition, in 48 of these patients who were methacholine responsive (PD20 < 1,000 microg), the acute protective effect of formoterol as a 24-microg single dose (at 1 h) was also evaluated. Comparisons were made according to homozygous and heterozygous (Het) polymorphisms at codon 16 and codon 27. RESULTS: There were no significant differences in age, FEV1 percent predicted, or inhaled corticosteroid dose, when comparing mean values for polymorphisms at either codon-16 or codon 27. There were also no significant differences between polymorphisms for any of the measured lymphocyte beta2-adrenoceptor parameters apart from basal cAMP between Glu-27 and Het-27. Mean values for Emax (after-before isoproterenol as pmol/10(6) cells) were as follows: Gly-16 (3.4), Arg-16 (3.5), Het-16 (4.0), Glu-27 (3.9), Gln-27 (3.5), and Het-27 (3.7). Polylorphism had no significant effect on formoterol protection as doubling dose shift in methacholine PD20 (geometric mean): Gly-16 (5.3), Arg-16 (5.4), Het-16 (4.6), Glu-27 (5.3), Gln-27 (5.3), Het-27 (4.5). CONCLUSIONS: Our results show that genetic polymorphism at codon 16 or 27 does not influence stimulated coupling of lymphocyte beta2-adrenoceptors and similarly did not influence the degree of functional antagonism exhibited by formoterol. Thus, a single dose of beta2-agonist when used on demand affords equal protection against bronchoprotection regardless of genetic polymorphism.

The effect of the neutral endopeptidase inhibitor drug, candoxatril, on circulating levels of two of the most potent vasoactive peptides.

AIMS: Candoxatril is a specific neutral endopeptidase (NEP) 24.11 inhibitor, and previous work has documented the effect of NEP inhibition on atrial and brain natriuretic peptides (ANP, BNP). The aim of the present study was to ascertain the effect of NEP inhibition on circulating levels of vasoactive peptides. METHODS: We studied seven patients with chronic heart failure who were randomized to receive candoxatril, candoxatril/captopril, captopril and placebo in a four way cross over, double-blind pattern. RESULTS: The mean circulating level of endothelin (ET) was increased 2 h after placebo (10 to 20 pg ml-1) and also calcitonin gene-related peptide (CGRP) (27 to 51 pg ml-1), but ANP levels changed little during this time (73 to 75 pg ml-1). Following candoxatril, however, ET (10 to 39 pg ml-1, P < 0.05), CGRP (34 to 99 pg ml-1, P < 0.05) and ANP (72 to 108 pg ml-1, P < 0.05) increased further. A similar result was observed following combined treatment with candoxatril and captopril. CONCLUSIONS: We conclude that neutral endopeptidase inhibition increases circulating plasma levels of ET and CGRP in addition to the natriuretic peptides.

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.

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.

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) degrees 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.

Hormonal and renal differences between low dose and high dose angiotensin converting enzyme inhibitor treatment in patients with chronic heart failure.

OBJECTIVE: To assess the differential effects of low dose (5 mg) and high dose (20 mg) lisinopril treatment on cardiovascular hormones, renal function, and blood pressure over 24 hours in patients with heart failure. DESIGN: Double-blind crossover study. SETTING: Department of Clinical Pharmacology, Ninewells Hospital and Medical School, Dundee. PATIENTS: 19 patients with chronic heart failure and left ventricular ejection fraction < or = 45%. RESULTS: Plasma concentrations of aldosterone and endothelin were lower on the 20 mg dose (plasma aldosterone mean at peak drug effect: 90.7 v 152.0 pg/ml, P < 0.001; mean at trough effect: 124.7 v 174.4 pg/ml, P < 0.01; plasma endothelin at trough effect 4.70 v 6.04 pmol/l, P = 0.03). Creatinine clearance was lower on 20 mg lisinopril (68.7 v 82.1 ml/min, P < 0.05). The area under the curve for diastolic blood pressure over 24 hours was significantly lower on 20 mg (mean difference 3.0 mm Hg, P = 0.04); for systolic blood pressure there was a similar trend (mean difference 5.7 mmHg, P = 0.05). Plasma concentrations of atrial natriuretic peptide (ANP) and B-type natriuretic peptide were similar for both doses; urinary excretion of ANP was lower on 20 mg (12.2 v 13.6 pmol, P < 0.05). CONCLUSIONS: These results indicate that within the usual therapeutic range, high doses of lisinopril cause greater suppression of selected cardiovascular hormones than low doses in heart failure, but are associated with lower creatinine clearance in some patients.

Effects of exogenous female sex-steroid hormones on lymphocyte beta 2-adrenoceptors in normal females.

We have previously shown that lymphocyte beta 2-adrenoceptors (AR) are under cyclical control of sex-steroid hormones with greater receptor density during the luteal phase of the menstrual cycle. It has also been postulated that abnormal cyclical regulation of beta 2-AR might be a possible mechanism for premenstrual asthma. The effects of exogenous female sex-steroid hormones on lymphocyte beta 2-AR function were studied in eight normal healthy females. They were evaluated at two successive menstrual cycles, during the follicular phase (day 1-6). They were randomized to receive single oral doses of either ethinyloestradiol 50 micrograms or medroxyprogesterone 10 mg in a cross-over study. Lymphocyte beta 2-AR parameters were evaluated at baseline (t0), 24 h (t24) and 72 h (t72) after ingestion. Baseline levels of progesterone and oestradiol were comparable on both cycles. Receptor density (Bmax) increased significantly (P < 0.01) from t0 after progesterone but not oestradiol at t 4: a 1.39-fold geometric mean difference (95% CI 0.96-2.00) between t24 vs t0. Receptor affinity (kd) and maximal cAMP response to isoprenaline (Emax) were not altered by either treatment. These results show that exogenous progesterone but not oestradiol, given during the follicular phase, significantly increased beta 2-AR. This, therefore, suggests that endogenous progesterone is probably responsible for previously observed increase in Bmax during the luteal phase of the female menstrual cycle. These findings may suggest possible therapeutic strategies for modulation of beta 2-AR in premenstrual asthma.

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.

Acute neurohormonal responses to hypoxaemia in man.

We have studied the integrated neuroendocrine and haemodynamic effects of acute hypoxaemia in ten healthy volunteers studied on two separate occasions. After reaching a resting haemodynamic state, subjects breathed either room air or a nitrogen/oxygen mixture which rendered arterial oxygen saturation between 75% and 80%. Measurements of pulmonary and systemic haemodynamics were made and blood samples taken at baseline and after 30 min breathing air or the hypoxic gas. Blood was assayed for plasma sodium and potassium, renin-angiotensin-aldosterone system activity, natriuretic peptides, cortisol and catecholamines. Hypoxaemia significantly increased heart rate, cardiac output and mean pulmonary artery pressure (Ppa), but not mean arterial pressure compared with normoxaemia. Although plasma renin activity, angiotensin II and cortisol were unaffected by hypoxaemia, plasma aldosterone fell significantly in comparison with normoxaemia. This was associated with an increase in plasma atrial natriuretic peptide (ANP) but not b-type natriuretic peptide (BNP) during hypoxaemia whilst no changes were observed during normoxaemia. The increase in plasma ANP correlated positively with the increase in Ppa. During hypoxaemia there is therefore dissociation of the renin-angiotensin-aldosterone system where plasma aldosterone decreased, despite there being no effects on plasma renin activity and angiotensin II or on plasma cortisol. This dissociation may be due to increased levels of ANP but not BNP having specific inhibitory effects on aldosterone biosynthesis. ANP increased in proportion to the degree of pulmonary vasoconstriction induced by hypoxaemia which may indicate a counter-regulatory role.

Acute effects of atrial natriuretic peptide on left ventricular diastolic function. a pulsed wave Doppler study in man.

Doppler echocardiographic indices of diastolic function and systemic haemodynamics were studied in response to infusions of atrial natriuretic peptide (0.5, 1, 2, 5 pmol.kg-1.min-1) and placebo (0.9% (w/v) saline) in ten normal male subjects. Compared with placebo, atrial natriuretic peptide infusion produced a significant and dose-related reduction in the isovolumic relaxation time [(mean and 95% CI) -5.9 (-9.2 to -2.6) ms (P < 0.01) at 5 pg.kg-1 min-1] and a significant increase in the ratio between early and late transmitral peak velocities [0.46 (0.02 to 0.89) (P < 0.05) at 5 pg.kg-1 min-1]. No significant changes in heart rate, blood pressure or aortic stroke distance were observed with infusion of atrial natriuretic peptide compared with placebo. These data suggest that pathophysiological plasma concentrations of atrial natriuretic peptide improve diastolic function by increasing the rate of myocardial relaxation.

Cyclosporin-induced renal vasoconstriction is augmented by frusemide and by angiotensin II in humans.

OBJECTIVE: To investigate the role of the renin-angiotensin-aldosterone system as a homoeostatic mechanism by examining whether mild activation of the renin-angiotensin-aldosterone system could enhance cyclosporin-induced renal vasoconstriction and hypertension. METHODS: We artificially activated the renin-angiotensin-aldosterone system by two means: by pretreatment with frusemide (40 mg/day orally for 2 days) and by administering exogenous angiotensin II (1 ng/kg per min intravenously). In both cases the levels of renin-angiotensin-aldosterone system activation achieved did not by themselves alter renal blood flow, glomerular filtration rate or blood pressure. We then examined the effect of cyclosporin (10 mg/kg twice a day orally) in the presence of the activated renin-angiotensin-aldosterone system in normal humans. RESULTS: Cyclosporin alone acutely altered neither glomerular filtration rate (760 versus 734ml, NS; area under the curve for placebo versus cyclosporin) nor effective renal plasma flow (4,163 versus 3,915 ml, NS; area under the curve for placebo versus cyclosporin). Co-administration of exogenous angiotensin II with cyclosporin induced a fall in effective renal plasma flow from baseline but no change in glomerular filtration rate. Frusemide pretreatment together with cyclosporin administration induced a fall in glomerular filtration rate and a fall in effective renal plasma flow. Neither exogenous angiotensin II nor frusemide pretreatment influenced the blood pressure rise induced by cyclosporin. The present findings demonstrate that renin-angiotensin-aldosterone system activation augments cyclosporin-induced renal vasoconstriction but not cyclosporin-induced systemic vasoconstriction. We suggest that the renin-angiotensin-aldosterone system suppression, which normally occurs with cyclosporin, may be a homoeostatic mechanism to help prevent cyclosporin-induced renal vasoconstriction. The renin-angiotensin-aldosterone system appears, however, to play little or no role in mediating or preventing the initial increase in blood pressure caused by cyclosporin. Furthermore, frusemide is commonly prescribed together with cyclosporin even though this combination has the potential to cause a marked increase in renal dysfunction.