Beta Adrenoreceptor Research Articles

Analysis of β1 and β2-adrenergic receptors polymorphism in patients with apical ballooning cardiomyopathy

Objective The aim of our study was to analyse the frequency of β1 and/or β2 adrenergic receptor polymorphisms in patients with takotsubocardiomyopathy (TTC).Methods and resultsβ1 and/or β2 adrenergic receptor polymorphisms in 61 patients with TTC were compared with 109 controls. The β1 adrenoreceptor (amino acid position 389) genotype frequencies were signifi cantly diff erent in the two groups; assuming a recessive model for the allelic variant coding for Arg on this position, the odds ratio was 3.14, 95% CI 1.55-6.37 (P= 0.0015). The β2 adrenoreceptor amino acid position 27 genotype was signifi cantly diff erent and assuming a recessive model for the allelic variant coding for Gln on this position, the odds ratio was 0.29, 95% CI 0.12-0.74 (P= 0.009).Conclusions This study showed for the fi rst time an association between TTC phenotype and β1 adrenoreceptor gene polymorphisms. Beta adrenoreceptors gene polymorphisms are probably disease modifi ers, and any risk estimate should be based on a combination of genotypes and on interactions with other genes and environmental features.

A pharmacokinetic study of a combination of beta adrenoreceptor antagonists – In the isolated perfused ovine eye

The treatment of posterior eye diseases, such as diabetic retinopathy and age-related macular degeneration, is of growing interest as the number of people affected by these conditions continues to rise. This study utilises the methods of cassette dosing and the perfused ovine eye model – to reduce animal usage and therefore animal time – to show that for a series of beta adrenoreceptor antagonists, lipophilicity is a key physicochemical property that governs drug distribution within the eye. Following intravitreal injection, lipophilic beta adrenoreceptor antagonists penetrate to the posterior eye, where they bind to the choroid and reside in the retina at greater concentrations than more hydrophilic beta adrenoreceptor antagonists, which preferentially penetrate to the anterior eye.

Genetic association between common beta-2 adrenoreceptor polymorphism and asthma severity in school-age children

Recent studies have suggested that polymorphism of the beta-2 adrenergic receptor (β2AR) gene at codon 16 affect an individual’s airway responsiveness. This study aimed to evaluate the association between beta-2 adrenoreceptor genotypes at position 16 and asthma severity among 59 school-aged children. They were divided into two groups: control group including 19 healthy children and 40 asthmatic children as the study group. The study group was also divided into 20 mild asthmatic children and the remaining 20 patients suffered from severe asthma. Blood samples were collected from Chest Department, Pediatrics Hospital, Ain Shams University, from February 2008 to March 2009. Molecular analysis was performed at Science Faculty, Ain Shams University, Cairo, Egypt. Venous blood sample were collected and genotyping of β2AR gene polymorphism at position 16 was identified by polymerase chain reaction–restriction fragment length polymorphism analysis, using the NcoI restriction enzyme. We found a highly statistically significant difference of polymorphisms’ distribution of β2AR gene at codon 16 among asthmatic patients and control subjects ( χ 2 = 11.904; P = 0.0026), also among severe asthmatics and mild/moderate asthmatics ( χ 2 = 10.108; P = 0.0064). There was a strong association of heterozygous Arg16Gly of β2AR with severe asthmatics rather than that in control subjects (70% vs. 5.3%, P < 0.001), with odd ratio (OR) 42 (95% confidence interval (CI): 4.520–390.297), the highest OR in heterozygous Arg16Gly (42) suggests a dominant mode of action of the heterozygous Arg16Gly in development of asthma severity. So, we concluded that heterozygous Arg16Gly of β2AR gene appeared to be an important genetic factor in the expression of asthma severity.

Comparison of various iron chelators used in clinical practice as protecting agents against catecholamine-induced oxidative injury and cardiotoxicity

Catecholamines are stress hormones and sympathetic neurotransmitters essential for control of cardiac function and metabolism. However, pathologically increased catecholamine levels may be cardiotoxic by mechanism that includes iron-catalyzed formation of reactive oxygen species. In this study, five iron chelators used in clinical practice were examined for their potential to protect cardiomyoblast-derived cell line H9c2 from the oxidative stress and toxicity induced by catecholamines epinephrine and isoprenaline and their oxidation products. Hydroxamate iron chelator desferrioxamine (DFO) significantly reduced oxidation of catecholamines to more toxic products and abolished redox activity of the catecholamine-iron complex at pH 7.4. However, due to its hydrophilicity and large molecule, DFO was able to protects cells only at very high and clinically unachievable concentrations. Two newer chelators, deferiprone (L1) and deferasirox (ICL670A), showed much better protective potential and were effective at one or two orders of magnitude lower concentrations as compared to DFO that were within their clinically relevant plasma levels. Ethylenediaminetetraacetic acid (EDTA), dexrazoxane (ICRF-187, clinically approved cardioprotective agent against anthracycline-induced cardiotoxicity) as well as selected beta adrenoreceptor antagonists and calcium channel blockers exerted no effect. Hence, results of the present study indicate that small, lipophilic and iron-specific chelators L1 and ICL670A can provide significant protection against the oxidative stress and cardiomyocyte damage exerted by catecholamines and/or their reactive oxidation intermediates. This potential new application of the clinically approved drugs L1 and ICL670A warrants further investigation, preferably using more complex in vivo animal models.

89. Src activation by beta adrenoreceptors is a key switch for microenvironmental regulation of tumor metastasis

89. Src activation by beta adrenoreceptors is a key switch for microenvironmental regulation of tumor metastasis

Eszopiclone facilitation of the antidepressant efficacy of fluoxetine using a social defeat stress model

This study analyzed the interaction of the sleep aid eszopiclone (ESZ) and antidepressant fluoxetine (FLX) on social defeat stress (SDS) in the mouse. Beta adrenoreceptors, brain-derived neurotrophic factor (BDNF) and cAMP response element binding protein (CREB) expression in the hippocampus and frontal cortex were also analyzed. Subjects were adult male ‘intruder’ C57/B6 mice that were exposed to a retired ‘resident’ male breeder ICR mouse in this animal's home cage for a 5min period for each of 10 consecutive days, and the resident established physical dominance. The following day, all animals were assigned to one of four drug treatment groups, and treatment was given for up to 18days: vehicle, ESZ only (3mg/kg), FLX (10mg/kg) only, or ESZ+FLX. A social interaction test was given on days 1, 5, 10, and 15 of drug treatment to assess SDS. Results showed that the ESZ+FLX group spent less time in avoidance zones during the interaction test at days 1 and 5, and more time in the interaction zone at day 5 compared to defeated mice given vehicle. All drug treatment groups spent more time in the interaction zone compared to defeated mice given vehicle on day 1 as well as day 10. SDS completely dissipated by the fourth interaction test according to both behavioral measures. Neurochemically, SDS did not produce changes in any marker analyzed. This study shows the combination of ESZ and FLX alleviated SDS, but a neurochemical correlate remains elusive.

Beta-2 adrenoreceptor gene polymorphisms and sympathetic outflow in humans

Previous association studies suggested that common polymorphisms of the beta-2 adrenoreceptor gene leading to glycine for arginine substitution at position 16 or glutamic acid for glutamine substitution at position 27 affect blood pressure. We reasoned that measurements of resting sympathetic nerve traffic could increase the sensitivity of defining a gene phenotype relationship. We studied 111 Caucasian subjects (70 men, 41 women) with blood pressure<140/90 mmHg. We measured electrocardiogram, beat-by-beat finger blood pressure, brachial blood pressure, and muscle sympathetic nerve activity (MSNA) using microneurography. We genotyped the functionally relevant polymorphisms of the beta-2 adrenoreceptor gene by means of allele-specific polymerase chain reaction. Sympathetic nerve traffic was similar regardless of genotypes. We obtained similar results when we quantified sympathetic nerve traffic as bursts/100 heart beats or as normalized burst area or when we adjusted resting sympathetic nerve traffic for gender, age, and blood pressure. The polymorphism at position 27 affects sympathetic regulation in men. Men with a Glu/Glu genotype had a significant positive correlation between blood pressure and MSNA. While our study was not sufficiently powered to detect subtle influences of genetic variability in the beta-2 adrenoreceptor gene on resting sympathetic nerve traffic, a large effect is unlikely. However the observation that beta-2 adrenoreceptor genotype may affect coupling between resting sympathetic nerve traffic and systolic blood pressure deserves to be tested in larger populations.

Beta-Adrenoreceptor Modulation of Metabolic, Endocrine and Immunologic Function During Critical Illness

Acute critical illness is characterized by a hypermetabolic and catabolic response where profound endocrine, metabolic and immunologic changes are initiated and sustained through the activation, in part, of beta-adrenergic receptors. The modulation of beta-adrenergic receptor mediated endocrine, immunological and metabolic control may be beneficial in sepsis through a number of mechanisms. However, the complex interaction between beta-adrenoreceptor-mediated, apparently disparate systems may confer both positive and negative clinical outcomes. Chronic cardiac failure and sepsis/critical illness share several similar endocrine, immunologic and metabolic pathological features. Beneficial beta-adrenergic modulation of various pathophysiological changes has been demonstrated in both experimental and clinical heart failure. Investigations in critical illness rarely take into account the role of beta-adrenoreceptor stimulation in patients with such co-morbidities, who are among the most vulnerable to sepsis. Despite similar phenotypes and possibly common mechanisms, few clinical studies have explored whether beta-adrenoreceptor modulation may confer outcome benefit during critical illness. Recent experimental and observational clinical data illustrate that carefully monitored, patient/subject-specific beta-adrenoreceptor modulation may provide a useful intervention to ameliorate the detrimental effects of hyperacute and/or prolonged beta-adrenergic receptor stimulation. Most notably, human studies demonstrate that (non-specific) beta-adrenoreceptor blockade does not increase inflammation, sepsis, or infectious episodes. Furthermore, hemodynamically tailored beta-1 adrenoreceptor antagonism improves outcome in experimental sepsis through novel cardiac and non-cardiac mechanisms. Understanding the dynamic complexity of beta-adrenergic physiology during critical illness offers further insights into the mechanisms underlying maladaptive metabolic and immunologic changes and potentially novel therapeutic interventions.

Polymorphism Trp64Arg of beta 3 adrenoreceptor gene: allelic frequencies and influence on insulin resistance in a multicenter study of Castilla-León.

The genetic variant (Trp64Arg) is a missense mutation located within the beta3 adrenoreceptor (Beta3AR). The aim of our study was to investigate the influence of Trp64Arg polymorphism in the Beta3AR gene on insulin resistance in obese patients and the allelic distribution of this polymorphismin a geographic area of Spain. A population of 264 obese patients was analyzed. A bioimpedance, blood pressure, an assessment of nutritional intake, and biochemical parameters were measured. The beta 3 adrenoreceptor gene polymorphism(Trp64Arg) was genotyped. Two hundred and twenty six patients (77 males/149 females) (85.6%) had the genotype Trp64/Trp64 (wild type group) with and average age of 41.12 +/- 13.1 years and 38 patients (16 males/22 females) Trp64/Arg64 (14.4%) (mutant type group) with an average age of 40.5 +/- 12.7 years. High frequencies of Arg64 allele were observed in Salamanca and Valladolid. In the mutant type group, HOMA (3.75 +/- 2.77 vs 5.27 +/- 5.4; p < 0.05) was higher than wild type group. The finding of this study is the association of the Trp64/Arg64 Beta3AR with higher levels of HOMA. Frequencies of this polymorphism are different among geographic areas.

Cardioprotection, attenuated systemic inflammation, and survival benefit of β1-adrenoceptor blockade in severe sepsis in rats*

To explore the hypothesis that beta-1 adrenoreceptor blockade may be protective through the attenuation of sympathetic hyperactivity and catecholaminergic inflammatory effects on cardiac and hepatic function. Prospective, randomized, controlled study. Animal laboratory in a university medical center. Male adult Wistar rats. Peripheral beta1-adrenoceptor blockade through daily intraperitoneal injection (metoprolol, 100 mg x kg(-1); atenolol, 6 mg x kg(-1)) or central nervous system beta1-adrenoceptor blockade (intracerebroventricular metoprolol, 25 microg) to achieve approximately 20% heart rate reduction in rats for 2 days before or after the induction of lethal endotoxemia, cecal ligation and puncture, or fecal peritonitis. Peripheral beta1-adrenoceptor blockade established for 2 days before lethal endotoxemia markedly improved survival in both metoprolol-treated (n = 16; log rank test, p = .002) and atenolol-treated (n = 15; p = .03) rats. Overall mortality in cecal ligation and puncture was similar between metoprolol (40%; n = 10) and saline (50%; n = 10) pretreatment (p = .56), but the median time to death was increased by 33 hrs in metoprolol-treated rats (p = .03). Metoprolol pretreatment reduced hepatic expression of proinflammatory cytokines and lowered plasma interleukin-6 (both p < .05). Myocardial protein expression of interleukin-18 and monocyte chemoattractant protein-1, key mediators of cardiac dysfunction in sepsis, were also reduced (p < .05). Peripheral beta1-adrenoceptor blockade commenced 6 hrs after lethal endotoxemia or fecal peritonitis did not improve survival. However, arterial blood pressure was preserved and left ventricular contractility restored similar to that found in nonseptic controls. Central nervous system beta1-adrenoceptor blockade (metoprolol) did not reduce plasma cytokines or mortality, despite enhancing parasympathetic tone. Peripheral beta1-adrenoceptor blockade offers anti-inflammatory and cardioprotective effects, with mortality reduction if commenced before a septic insult. Its role in sepsis should be explored further.

Differential Association of Phosphodiesterase 4D Isoforms with β2-Adrenoceptor in Cardiac Myocytes

cAMP and protein kinase A (PKA) activation represents a key signaling mechanism upon beta-adrenergic stimulation under stress. Both beta(1)- and beta(2)-adrenoreceptor (ARs) subtypes induce cAMP accumulation, yet play distinct roles in cardiac contraction and myocyte apoptosis. Differences in controlling cAMP/PKA activities through the assembly of complexes between the receptors and cAMP-specific phosphodiesterases contribute to the distinct biological outcomes. Here, we demonstrate that beta(2)ARs form signaling complexes with a set of PDE4D isoforms expressed in cardiac myocytes. PDE4D9 and PDE4D8 bind to the beta(2)AR at resting conditions; however, agonist stimulation induces dissociation of PDE4D9 from the receptor but recruitment of PDE4D8 to the receptor. Agonist stimulation also induces recruitment of PDE4D5 to the beta(2)AR. Moreover, the receptor-associated PDE4D isoforms play distinct roles in controlling cAMP activities and regulating the PKA phosphorylation of the receptor and myocyte contraction rate responses. Knockdown of PDE4D9 with short hairpin RNA enhances the beta(2)AR-induced cAMP signaling, whereas knockdown of PDE4D8 only slightly prolongs the receptor-induced cAMP signaling in myocytes. Inhibition of PDE4D9 and PDE4D5 enhances the base-line levels of contraction rates, whereas inhibition of PDE4D9 and PDE4D8 enhances the maximal contraction rate increases upon activation of beta(2)AR. Our data underscore the complex regulation of intracellular cAMP by beta(2)AR-associated phosphodiesterase enzymes to enforce the specificity of the receptor signaling for physiological responses.

Increased vagal airway tone in fatal asthma

Slow-onset asthma deaths are characterized by eosinophilic airway infiltrates and thickening of the basal membrane, while rapid-onset asthma deaths are associated with fewer airway inflammatory changes, suggesting that bronchospasm may be responsible for the latter events. Airway tone is primarily controlled by the autonomous nervous system and can be pharmacologically modified. Therapies that stimulate the sympathetic beta(2) adrenoreceptor or inhibit the muscarinic receptor signal transduction induce bronchodilation. Parasympathetic (vagal) airway tone is enhanced in some asthmatics due to a number of stimuli, while in others it is constitutively heightened. Mainstream asthma therapy, however, only consists of corticosteroids and beta(2) agonists, not addressing this aspect. In this publication, I propose that increased vagal airway tone resulting in overwhelming bronchoconstriction and mucus plugging could be responsible for the near-fatal or fatal events observed in a number of asthmatics, in spite of their adequate treatment with standard therapies. On the basis of this hypothesis, I recommend that vagal airway tone be assessed in all patients with asthma, particularly in those with a history of near-fatal events. If the airway tone is increased, individuals should be treated with a triple combination of long-acting beta(2) agonists, inhaled steroids, and inhaled anticholinergics to prevent vagally mediated fatal events.

Chronic effects assessment and plasma concentrations of the β-blocker propranolol in fathead minnows ( Pimephales promelas)

The presence of many human pharmaceuticals in the aquatic environment is now a worldwide concern, yet little is known of the chronic effects that these bioactive substances may be having on aquatic organisms. Propranolol, a non-specific beta adrenoreceptor blocker (β-blocker), is used to treat high blood pressure and heart disease in humans. Propranolol has been found in surface waters worldwide at concentrations ranging from 12 to 590 ng/L. To test the potential for ecologically relevant effects in fish in receiving waters, short-term (21 days) adult reproduction studies were conducted, in which fathead minnows were exposed to nominal concentrations of propranolol hydrochloride [CAS number 318-98-9] ranging from 0.001 to 10 mg/L (measured concentrations typically from 78 to 130%). Exposure of fish to 3.4 mg/L (measured) over 3 days caused 100% mortality or severe toxicity requiring euthanasia. The most sensitive endpoints from the studies were a decrease in hatchability (with regard to the number of days to hatch) and a concentration-related increase in female gonadal somatic index (GSI), giving LOEC hatchability and LOEC female GSI values of 0.1 mg/L. Concentration-related decreases in weights of male fish were also observed, with LOEC male wet weight value of 1.0 mg/L, and the LOEC reproduction value was 1.0 mg/L. Collectively, these data do not suggest that propranolol was acting as a reproductive toxin. Plasma concentrations of propranolol in male fish exposed to nominal concentrations of 0.1 and 1.0 mg/L were 0.34 and 15.00 mg/L, respectively, which constitutes 436 and 1546% of measured water concentrations. These compare with predicted concentrations of 0.07 and 0.84 mg/L, and thus to a degree support the use of partition coefficient models for predicting concentrations in plasma in fish. In addition, propranolol plasma concentrations in fish exposed to water concentrations of 0.1 and 1.0 mg/L were greater than the human therapeutic plasma concentration and hence these data very strongly support the fish plasma model proposed by Huggett et al. [Huggett, D.B., Cook, J.C., Ericson, J.F., Williams, R.T., 2003a. A theoretical model for utilizing mammalian pharmacology and safety data to prioritize potential impacts of human pharmaceuticals to fish. Hum. Ecol. Risk Assess. 9, 1789–1799].

Changes in components of left ventricular mechanics under selective beta-1 blockade: insight from traditional and new technologies in echocardiography

Myocardial inotropism is considered to be reduced under beta-1 adrenoreceptor blockage (beta1-block). However, relationships between components of left ventricular (LV) systolic mechanics under beta1-block accounting for physiological correlates are only partially explored. Hypertensive outpatient without previous cardiovascular events and with normal LV ejection fraction (EF) at rest underwent echocardiographic evaluations of LV size and systolic function by standard, tissue-Doppler, and speckle-tracking methods before and after 2 weeks of treatment with bisoprolol to obtain change in LV systolic mechanics at a stable heart rate reduction (-20 +/- 10% from baseline) without significant change in LV mass. In the study sample (n = 26, 62% women, mean age 52 +/- 10 years), under bisoprolol, afterload [i.e. circumferential (CESS) and meridional (MESS) end-systolic stress], LV mass, left atrial volume, and EF did not change significantly; LV chamber contractility [i.e. CESS/LV end-systolic volume index (CESS/ESVi) as well as MESS/ESVi] and relative wall thickness (RWT) decreased; stroke volume increased (all P < 0.05). Circumferential LV contractility (i.e. stress-corrected midwall shortening) increased, whereas regional longitudinal strain and strain rate, and global longitudinal strain decreased (all P < 0.05). Peak velocities of the systolic displacement of the lateral and medial mitral anulus did not change under bisoprolol. Parameters of longitudinal LV systolic function did not correlate with preload, afterload, RWT, or with stoke volume. In hypertensive subjects with preserved LV EF, parameters of longitudinal LV systolic mechanics may not reflect the LV myocardial contractility status in steady-state conditions under short-term treatment with beta1-block.

Synthesis and properties of a new conformational antigen which models an extracellular region of β1-adrenoreceptor

Two fragments corresponding to the 125-133 and 206-218 sequences of a molecule of the beta(1) adrenoreceptor (autoantibodies to this protein are often found in patients with dilated cardiomyopathy) were synthesized by the solid phase method with the use of Fmoc technology. Two new conformational antigens were prepared by directed (regioselective) and undirected (spontaneous) formation of intramolecular and intermolecular disulfide bridges between the corresponding cysteine residues of the synthesized peptides. One of these antigens consisted of a mixture of disulfide isomers, and another antigen was an isomer with a natural arrangement of S-S bridges. Immunosorbents were obtained by immobilization of the synthesizes antigens on the bromocyanogenactivated sepharose and applied to the removal of autoantibodies in a beta(1)-adrenoreceptor from the blood plasma of patients. We demonstrated that the sorbents on the basis of the conformational antigens were more effective in comparison with those containing linear peptide precursors.

Additive role of tiotropium in severe asthmatics and Arg16Gly in ADRB2 as a potential marker to predict response

Recent findings have raised new interests about the use of anticholinergics, especially tiotropium, for the treatment of asthma. This study was performed to determine whether an additional improvement in lung function is obtained when tiotropium is administrated in addition to conventional therapies in severe asthmatics, and to identify factors capable of predicting the response to tiotropium, using a pharmacogenetic approach. A total of 138 severe asthmatics on conventional medications and with decreased lung function were randomly recruited. Tiotropium 18 microg was added once a day and lung functions were measured every 4 weeks. Responders were defined as those with an improvement of > or = 15% (or 200 ml) in the forced expiratory volume in 1 s (FEV1) that was maintained for at least 8 successive weeks. Eleven single nucleotide polymorphisms (SNPs) in CHRM1-3 (coding muscarinic receptors one to three) which were identified by re-sequencing, and Arg16Gly and Gln27Glu in ADRB2 (coding beta(2) adrenoreceptor) were scored in 80 of the 138 asthmatics. Forty-six of the 138 asthmatics (33.3%) responded to tiotropium treatment. Logistic regression analyses (controlled for age, gender, and smoking status) showed that Arg16Gly in ADRB2 [P = 0.003, OR (95% CI) = 0.21 (0.07-0.59) in a minor allele-dominant model] was significantly associated with response to tiotropium. As many as 30% of severe asthmatics on conventional medications with reduced lung function were found to respond to adjuvant tiotropium. The presence of Arg16Gly in ADRB2 may predict response to tiotropium.

Influence of Trp64Arg Polymorphism of Beta 3-Adrenoreceptor Gene on Insulin Resistance, Adipocytokines and Weight Loss Secondary to Two Hypocaloric Diets

Objective: To investigate the influence of the Trp64Arg polymorphism in the beta 3-adrenoreceptor gene on adipocytokines, insulin resistance and weight loss secondary to a low fat versus a low carbohydrate diet. Methods: A population of 193 obese patients was analyzed. A nutritional evaluation was performed at the beginning and at the end of a 2-month period in which subjects received 1 of 2 hypocaloric diets. Results: 172 (89.1%; 44 males, 128 females) subjects had the genotype Trp64/Trp64 (wild-type group) and 21 subjects (10.9%; 4 males, 17 females) had Trp64/Arg64 (mutant-type group). In the wild-type group BMI, weight, fat mass, waist circumference, systolic blood pressure, glucose, triglycerides, insulin, homeostasis model assessment (HOMA) and leptin decreased significantly regardless of the diet. In the mutant-type group, this was the case for BMI, weight, waist circumference, fat mass and leptin levels. Only leptin levels have a significant decrease in the wild-type group (diet I 13.7%, diet II 26.3%, p < 0.05 for both). In the mutant group, leptin decreased as well (diet I 22.5%, diet II 30.1%, p < 0.05 for both). Conclusion: The metabolic effect of mild weight reduction by 2 hypocaloric diets is greatest in subjects homozygous for the normal beta 3-adrenoreceptor gene. Improvement in glucose, insulin and HOMA is better than in the mutant-type group.

A novel breath-actuated integrated vortex spacer device increases relative lung bioavailability of fluticasone/salmeterol in combination

Background Spacer devices facilitate respirable drug delivery. A novel breath-actuated antistatic spacer with integrated vortex chamber (Synchro-Breathe™) device has been developed, which is compact, portable and user friendly as compared to conventional spacers which are bulky and cumbersome. The relative bioavailability to the lung of inhaled fluticasone and salmeterol combination is primarily dependant on respirable dose delivery and can be reliably quantified using adrenal suppression and early fall in serum potassium (marker of systemic beta-2 adrenoreceptor response) as surrogate markers for delivered lung dose. Aims and objectives To compare the in vivo relative bioavailability to the lung of Hydrofluoroalkane (HFA) Seretide™ delivered via Synchro-Breathe (SB); an optimally prepared 750 ml large volume plastic spacer, Volumatic™ (VM); and conventional Evohaler pMDI (EH). Methods Nineteen healthy volunteers completed the study using a randomised double blind, double dummy crossover design. Single doses of placebo or Seretide HFA 250 (total dose ex-valve: fluticasone 2000 mcg/salmeterol 200 mcg) were administered via SB, VM and EH. Overnight urinary cortisol creatinine (OUCC) and serum potassium (K) were measured at baseline and after each dose as systemic surrogates of relative respirable dose delivery for the fluticasone and salmeterol moieties, respectively. Results Significant suppression of OUCC and K occurred from baseline with SB and VM but not EH devices (geometric mean fold suppression, 95% CI, p and arithmetic mean fall mmol/L, 95% CI, respectively); EH: 1.51(0.43–1.01), p = 0.06; VM: 2.52(1.57–4.04), p < 0.001; SB: 2.66(1.57–4.49), p < 0.001(equating to 33.8%, 60.2% and 62.3% falls, respectively). For K, the falls for EH were −0.09(−0.25 to 0.07), p = 0.69; VM: −0.27(−0.46 to −0.08), p = 0.003; SB: −0.32(−0.53 to −0.11), p = 0.002 (equating to 2.2%, 6.8%, and 8.06% fall, respectively). There were no significant differences between SB and VM. Conclusion The breath-actuated Synchro-Breathe device was comparable to an optimally prepared Volumatic spacer, and resulted in commensurate improvement in relative lung bioavailability for both fluticasone and salmeterol moieties compared to pMDI.

INCREASED AEROBIC GLYCOLYSIS THROUGH β2 STIMULATION IS A COMMON MECHANISM INVOLVED IN LACTATE FORMATION DURING SHOCK STATES

During septic shock, muscle produces lactate by way of an exaggerated NaK-adenosine triphosphatase (ATPase)-stimulated aerobic glycolysis associated with epinephrine stimulation possibly through beta2 adrenoreceptor involvement. It therefore seems logical that a proportion of hyperlactatemia in low cardiac output states would be also related to this mechanism. Thus, in low-flow and normal-to-high-flow models of shock, we investigate (1) whether muscle produces lactate and (2) whether muscle lactate production is linked to beta2 adrenergic stimulation and Na+K+-ATPase. We locally modulated the adrenergic pathway and Na+K+-ATPase activity in male Wistar rats' skeletal muscle using microdialysis with nonselective and selective beta blockers and ouabain in different models of rodent shock (endotoxin, peritonitis, and hemorrhage). Blood flow at the probe site was evaluated by ethanol clearance. We measured the difference between muscle lactate and blood lactate concentration, with a positive gradient indicating muscle lactate or pyruvate production. Epinephrine levels were elevated in all shock groups. All models were associated with hypotension and marked hyperlactatemia. Muscle lactate concentrations were consistently higher than arterial levels, with a mean gradient of 2.5+/-0.3 in endotoxic shock, 2.1+/-0.2 mM in peritonitis group, and 0.9+/-0.2 mM in hemorrhagic shock (P<0.05 for all groups). Muscle pyruvate concentrations were also always higher than arterial levels, with a mean gradient of 260+/-40 microM in endotoxic shock, 210+/-30 microM in peritonitis group, and 90+/-10 microM in hemorrhagic shock (P<0.05 for all groups). Despite a decrease in blood flow, lactate formation was decreased by all the pharmacological agents studied irrespective of shock mechanism. This demonstrates that lactate production during shock states is related, at least in part, to increased NaK-ATPase activity under beta2 stimulation. In shock state associated with a reduced or maintained blood flow, an important proportion of muscle lactate release is regulated by a beta2 receptor stimulation and not secondary to a reduced oxygen availability.

Stimulating Effects of Dopamine on Chloride Transport Across the Rat Caudal Epididymal Epithelium in Culture1

The present study investigated the effects of dopamine on chloride transport across cultured rat caudal epididymal epithelium. The results showed that dopamine induced a biphasic short-circuit current (Isc) in a concentration-dependent manner. The dopamine-induced response consisted of an initial rapid spike followed by a sustained phase. The alpha and beta adrenoreceptor inhibitors, phentolamine and propranolol, inhibited the initial spike and the sustained phase, respectively, suggesting a contribution of adrenergic receptors. The response was almost abolished by removing the extracellular Cl-, suggesting that the dopamine-induced short-circuit current is primarily a Cl- current. The response was inhibited by the apical Cl- channel blocker, diphenylamine-dicarboxylic acid, and the Ca2+-activated Cl- channel blocker, disulfonic acid stilbene, indicating that Cl- may pass through two types of Cl- channels on the apical side. Preloading monolayers with the intracellular Ca2+ chelator BAPTA/AM abolished the initial spike and greatly reduced the second phase in the Isc response to dopamine. Pretreating the monolayers with an adenylate cyclase inhibitor, MDL12330A, inhibited all of the second Isc response and part of the initial spike. Also, characteristics of the Cl- currents induced by dopamine were observed in whole-cell patch-clamp recording. The increases of intracellular cAMP and Ca2+ induced by dopamine were also measured. The results suggest that extracellular dopamine activates Ca2+-dependent and cAMP-dependent regulatory pathways, leading to activation of both Ca2+-dependent and cAMP-dependent Cl- conductances in epididymal epithelial cells.