A large number of β-adrenergic receptor (β-AR) agonists and antagonists are widely used in the treatment of cardiovascular diseases and other diseases. Nonetheless, it remains unclear whether these commonly used β-AR drugs can activate downstream β- arrestin-biased signaling pathways. The objective of this study was to investigate β-arrestin2 recruitment effects of β-AR agonists and antagonists that were commonly used in clinical practice. We used TANGO (transcriptional activation following arrestin translocation) assay to detect the β-arrestin2 recruitment by β-AR ligands in HEK293 cell line (HTLA cells) stably transfected with tetracycline transactivator protein (tTA) dependent luciferase reporter and β-arrestin2-TEV fusion gene. Upon activation of β-AR by a β-AR ligand, β-arrestin2 was recruited to the C terminus of the receptor, followed by cleavage of the G protein-coupled receptors (GPCRs) fusion protein at the TEV protease-cleavage site. The cleavage resulted in the release of tTA, which, after being transported to the nucleus, activated transcription of the luciferase reporter gene. The results showed that β-AR non-selective agonists epinephrine, noradrenaline and isoprenaline all promoted β-arrestin2 recruitment at β1-AR and β2-AR. β1-AR selective agonists dobutamine and denopamine both promoted β-arrestin2 recruitment at β1-AR. β2-AR selective agonists procaterol and salbutamol promoted β-arrestin2 recruitment at β2-AR. β-AR non-selective antagonists alprenolol and pindolol promoted β-arrestin2 recruitment at β1-AR. β1-AR selective antagonists celiprolol and bevantolol showed β-arrestin2 recruitment at β1-AR. β2-AR selective antagonists butoxamine showed β-arrestin2 recruitment at β1-AR. These results provide some clues for the potential action of β-AR drugs, and lay a foundation for the screening of β-arrestin-biased β-AR ligands.
Humans ; beta-Arrestin 2/metabolism* ; HEK293 Cells ; Adrenergic beta-Agonists/pharmacology* ; Isoproterenol/pharmacology* ; Receptors, Adrenergic, beta-2/metabolism* ; Norepinephrine/pharmacology*

To examine the role of nitric oxide in the beta-adrenergic vasodilation of epicardial coronary arteries in dogs, 12 dogs were instrumented for measurement of left anterior descending coronary artery diameter by transthoracic echocardiography before and after dobutamine (5 microg/kg/min IV) with and without intracoronary infusion of NG-monomethyl-L-arginine (L-NMMA) (1 mg/kg). In all 12 dogs, the diameter of left anterior descending coronary artery increased significantly from 2.35 +/- 0.25 mm to 2.59 +/- 0.24 mm (P<0.001) after dobutamine administration. In 6 of the 12 dogs, the percent change in left anterior descending coronary artery diameter induced by dobutamine decreased significantly from 12.5% +/- 8.6% to -1.5% +/- 5.4% (P<0.05) after the administration of intracoronary L-NMMA (1 mg/kg for 5 min) to block nitric oxide synthesis from L-arginine. The study demonstrated that nitric oxide formation contributes to the beta-adrenergic dilatory response of epicardial coronary arteries to dobutamine in dogs.
Adrenergic beta-Agonists ; pharmacology ; Animals ; Coronary Vessels ; physiology ; Dobutamine ; pharmacology ; Dogs ; Echocardiography ; Female ; Male ; Nitric Oxide ; physiology ; Receptors, Adrenergic, beta ; physiology ; Vasodilation ; physiology ; omega-N-Methylarginine ; pharmacology

OBJECTIVETo study the interactions between Ligusticum chuanxiong Hort extract and cardiac muscle membrane receptors.

METHODThe cell membrane of rabbit cardiac muscle was fixed on silicon to make cell membrane stationary phase (CMSP), and then the interactions were studied by comparing the retention characteristics of the extracts from different solvents with those of the antagonists or activators corresponding to known receptors in cardiac muscle membrane, and by competition effect on the retention characteristics of extracts when adding the antagonists or activators into the mobile phase.

RESULTWater extract and ethanol extract both had retentions on CMSP; the retention characteristics of water extract could be affected when water extract was in competition with the antagonists for alpha receptor, and could not be affected when with the activator beta1 receptor.

CONCLUSIONIt is possible that some components in water extract may combine with alpha receptor and no component with beta1 receptor, and that some components in ethanol extract may combine with cardiac muscle cell membrane. The process between active components and receptors in vivo can be imitated through the interactions between drugs and CMSP. The method provides references for the resolution of two applications: to screen the active components from Chinese medicine, and to figure out the type of receptors involved.

Adrenergic alpha-Agonists ; metabolism ; Adrenergic alpha-Antagonists ; metabolism ; Adrenergic beta-Agonists ; metabolism ; Adrenergic beta-Antagonists ; metabolism ; Animals ; Cell Membrane ; metabolism ; Chromatography, High Pressure Liquid ; methods ; Drugs, Chinese Herbal ; isolation & purification ; pharmacology ; Female ; Ligusticum ; chemistry ; Male ; Myocytes, Cardiac ; cytology ; metabolism ; Plants, Medicinal ; chemistry ; Protein Binding ; Rabbits ; Receptors, Adrenergic, alpha ; metabolism ; Receptors, Adrenergic, beta ; metabolism

OBJECTIVETo observe the effects of combined beta(1) adrenergic receptor (AR) antagonist with beta(2)AR agonist therapy on cardiac function and cardiomyocyte apoptosis in heart failure rats.

METHODSHeart failure was induced by isoproterenol and rats were randomly divided into metoprolol group (50 mg/kg twice daily/gavage, n = 11), combined treatment group (fenoterol 125 microg/kg and metoprolol 50 mg/kg twice daily/gavage, n = 11) and placebo group (saline, n = 10), another normal 9 male Wistar rats served as control group. After 8 weeks' treatment, cardiac function, apoptosis index (AI), Caspase-3 activity, expression levels of bcl-2 and bax protein, organ weight/body weight and collagen volume fraction (CVF) were evaluated.

RESULTS(1) Left ventricular end diastolic dimension, left ventricular end systolic dimension and E/A ratio were significantly increased and fractional shortening, ejection fraction significantly reduced post isoproterenol (all P < 0.05 vs. control) and these changes were significantly attenuated by metoprolol alone (all P < 0.05 vs. placebo) and further attenuated by the metoprolol and fenoterol combination therapy (all P < 0.05 vs. placebo and metoprolol). (2) Left ventricular weight to body weight ratio, lung weight to body weight ratio and CVF were also significantly reduced in metoprolol and combined treatment group than those in placebo group (all P < 0.01). (3) Compared with placebo group, AI and Caspase-3 activity were significantly lower in metoprolol group (all P < 0.01 vs. placebo) and further reduced in combined treatment group (all P < 0.01 vs. metoprolol). (4) The expression level of bax protein was significantly lower in metoprolol group while bcl-2/bax significantly higher than those in placebo group. These changes were more significant in combined treatment group (all P < 0.01 vs. metoprolol).

CONCLUSIONSbeta(1)AR antagonist in combination with beta(2)AR agonist further improved the cardiac function and prevented cardiac remodeling compared with using beta(1)AR antagonist alone in heart failure rats. Downregulated bax and upregulated bcl-2/bax expressions might contribute to the observed beneficial therapy effects by reducing cardiomyocyte apoptosis in these animals.

Adrenergic beta-1 Receptor Antagonists ; Adrenergic beta-2 Receptor Agonists ; Adrenergic beta-Agonists ; pharmacology ; therapeutic use ; Adrenergic beta-Antagonists ; pharmacology ; therapeutic use ; Animals ; Apoptosis ; drug effects ; Drug Therapy, Combination ; Heart Failure ; drug therapy ; Male ; Myocytes, Cardiac ; cytology ; Rats ; Rats, Wistar ; Ventricular Remodeling

To evaluate the effects of left ventricular contractility on the changes of average image intensity (AII) of the myocardial integrated backscatter (IB) and cyclic variation in IB (CVIB), 7 adult mongrel dogs were studied. The magnitude of AII and CVIB were measured from myocardial IB carves before and after dobatamine or propranolol infusion. Dobutamine or propranolol did not affect the magnitude of AII (13.8 +/- 0.7 vs 14.7 +/- 0.5, P > 0.05 or 14.3 +/- 0.5 vs 14.2 +/- 0.4, P > 0.05). However, dobutamine produced a significant increase in the magnitude of CVIB (6.8 +/- 0.3 vs 9.5 +/- 0.6, P < 0.001) and propranolol induced significant decrease in the magnitude of CVIB (7.1 +/- 0.2 vs 5.2 +/- 0.3, P < 0.001). The changes of the magnitude of AII and CVIB in the myocardium have been demonstrated to reflect different myocardial physiological and pathological changes respectively. The alteration of contractility did not affect the magnitude of AII but induced significant change in CVIB. The increase of left ventricular contractility resulted in a significant rise of the magnitude of CVIB and the decrease of left ventricular contractility resulted in a significant fall of the magnitude of CVIB.
Adrenergic beta-Agonists ; pharmacology ; Adrenergic beta-Antagonists ; pharmacology ; Animals ; Coronary Circulation ; Dobutamine ; pharmacology ; Dogs ; Echocardiography ; methods ; Hemodynamics ; drug effects ; Myocardial Contraction ; drug effects ; physiology ; Propranolol ; pharmacology ; Systole ; Ventricular Function, Left ; physiology

AIMTo evaluate the effects of beta3-adrenergic receptors (ARs) agonist (BRL-37344) on beating rate and cAMP levels and investigate the influence on the chronotropic action of beta3-ARs in cultured cardiomyocyte of rats.

METHODSCultured neonatal rat cardiomyocytes were divided randomly into eight groups, control group, ISO group, Nadolol + ISO group, BRL group, PIX + BRL group, L-NAME + BRL group, Nadolol + BRL group and Bupranolol + BRL group. Beating rate of culture neonatal rat cardiomyocytes was observed and cAMP measured by enzyme immunoassay kit. Expression levels of beta3-ARs mRNA in cardiomyocytes was evaluated by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTSISO, nonspecific beta-ARs agonist increased beating rate and intracellular cAMP production, antagonized by Nadolol, beta1, beta2-ARs antagonist. BRL37344 decreased beating rate and intracellular cAMP levels. FPTX, Gi protein inhibitor and Bupranolol, nonspecific beta-ARs antagonist totally blocked the effect and L-NAME, nitric oxide synthase (NOS) inhibitor partly blocked the effect, but Nadolol did not. There was the expression of beta3-AR mRNA in cardiomyocytes by RT-PCR.

CONCLUSIONSBeta3-ARs showed in cardiomyocytes and produced negative chronotropic effects. beta1, beta2-ARs antagonist did not affect it. It suggested beta3-ARs signal transduction was related with G1 protein. The negative inotropic effect of beta3-ARs stimulation was mediated by activation of the NOS pathway.

Adrenergic beta-Agonists ; pharmacology ; Animals ; Animals, Newborn ; Cells, Cultured ; Cyclic AMP ; metabolism ; Ethanolamines ; pharmacology ; Myocytes, Cardiac ; drug effects ; metabolism ; RNA, Messenger ; genetics ; Rats ; Rats, Wistar ; Receptors, Adrenergic, beta-3 ; metabolism

We investigated the effect of beta-adrenergic stimulation on the heart rate and QT interval in syncope children with or without coexisting ventricular arrhythmias (VA). Of the 24 children who presented with syncope or presyncope and showed negative tilt test, 13 were classified into a group with VA and the remaining 11 without VA. The provocative test was performed in bolus infusion and continuous infusion. RR, QT, and QTc intervals on routine 12-lead surface electrocardiogram were obtained during each stage of isoproterenol infusion. In all cases, malignant ventricular arrhythmia and syncope were not induced by isoproterenol provocative test. RR and QT intervals were shortened and QTc intervals were prolonged as the isoproterenol dose was increased in both groups and methods. The QTc interval reached its peak level after the bolus injection of 1.0 microgram and during the continuous infusion of 0.03 microgram/kg/min. The two groups showed no significant difference in the QTc interval change according to the infusion methods. This study indicates that changes in the heart rate and QT interval by beta-adrenergic stimulation were not different according to the coexisting ventricular arrhythmias in syncope children with negative head-up tilt test.
Adolescent ; Adrenergic beta-Agonists/pharmacology* ; Arrhythmia/physiopathology* ; Child ; Child, Preschool ; Comorbidity ; Electrocardiography ; Female ; Heart Rate/drug effects* ; Heart Rate/physiology* ; Human ; Isoproterenol/pharmacology* ; Male ; Syncope/physiopathology*

OBJECTIVEImpaired active fluid transport of alveolar epithelium may involve in the pathogenesis and resolution of alveolar edema. The objective of this study was to explore the changes in alveolar epithelial liquid clearance during lung edema following acute lung injury induced by oleic acid.

METHODSForty-eight Wistar rats were randomly divided into six groups, i.e., injured, amiloride, ouabain, amiloride plus ouabain and terbutaline groups. Twenty-four hours after the induction of acute lung injury by intravenous oleic acid (0.25 ml/kg), 5% albumin solution with 1.5 microCi (125)I-labeled albumin (5 ml/kg) was delivered into both lungs via trachea. Alveolar liquid clearance (ALC), extravascular lung water (EVLW) content and arterial blood gases were measured one hour thereafter.

RESULTSAt 24 h after the infusion of oleic acid, the rats developed pulmonary edema and severe hypoxemia, with EVLW increased by 47.9% and ALC decreased by 49.2%. Addition of either 2x10(-3) M amiloride or 5x10(-4) M ouabain to the instillation further reduced ALC and increased EVLW. ALC increased by approximately 63.7% and EVLW decreased by 46.9% with improved hypoxemia in the Terbutaline (10(-4) M) group, compared those in injured rats. A significant negative correlation was found between the increment of EVLW and the reduction of ALC.

CONCLUSIONSActive fluid transport of alveolar epithelium might play a role in the pathogenesis of lung edema in acute lung injury.

Adrenergic beta-Agonists ; pharmacology ; Animals ; Epithelium ; metabolism ; Oleic Acid ; adverse effects ; Pulmonary Alveoli ; metabolism ; Random Allocation ; Rats ; Rats, Wistar ; Respiratory Distress Syndrome, Adult ; chemically induced ; metabolism ; Terbutaline ; pharmacology

OBJECTIVETo study age-dependent changes in beta-adrenergic responsiveness and their possible mechanisms.

METHODSResponsiveness to the beta-adrenergic agonists isoprenaline, BRL37344, forskolin, and dibutyryl cyclic AMP (DBcAMP) was examined in samples from 10 older patients by using a cellular function test. A radioligand binding assay was performed using the non-selective beta-adrenergic receptor ligand [3H]-dihydroalprenolol ([3H]-DHA). Specimens from 10 young men were used as controls.

RESULTSThere were no age-dependent changes in contractile response to KCl. The relaxation responses to isoprenaline, BRL37344, and forskolin decreased in the aged group by 15.0%, 17.6%, and 12.6%, respectively (P < 0.001). The pD2 values for isoprenaline and BRL37344 also declined significantly. There was no difference in the responsiveness to dibutyryl cyclic AMP (DBcAMP) between the two groups; the maximum binding site decreased significantly with increasing age, but the equilibrium-dissociation constant did not change.

CONCLUSIONSThere is an age-related decline in beta-adrenergic responsiveness which might be one of the causative factors of reduced bladder compliance in the elderly. A decrease in cAMP level caused by reduced receptor density and adenylyl cyclase activity might be the underlying molecular mechanism of the changes in beta-adrenergic responsiveness.

Adrenergic beta-Agonists ; pharmacology ; Age Factors ; Aged ; Aging ; physiology ; Female ; Humans ; Male ; Middle Aged ; Muscle Contraction ; physiology ; Muscle, Smooth ; physiology ; Radioligand Assay ; Receptors, Adrenergic, beta ; physiology ; Urinary Bladder ; physiology

AIMTo study the effects of beta 2-adrenergic receptor-selective agonist clenbuterol on nitrogen metabolism and glucose-6-phosphate dehydrogenase activity of rat hepatocyte and its pharmacological mechanism.

METHODSBiochemical methods were used to study the influence of clenbuterol on urea-nitrogen concentration of hepatocyte culture medium, 3H-leucine incorporation into hepatocyte, insulin-like growth factor I (IGF-I) production and glucose-6-phosphate dehydrogenase (G6PDH) activity of rat hepatocyte.

RESULTSThe results showed that urea-nitrogen production by cultured rat hepatocytes was markedly affected with clenbuterol treatment (1 x 10(-6) mol.L-1), urea-nitrogen concentration of culture medium was decreased by 25.51% (P < 0.05) compared with control. The inhibitory effect of hepatocyte urea-nitrogen production of clenbuterol was blocked by propranolol, a beta-adrenoreceptor antagonist (1 x 10(-6) mol.L-1), but hepatocyte urea-nitrogen level was not affected with propranolol treatment only (P > 0.05). The content of 3H-leucine incorporation in rat hepatocyte was significantly increased by 23.35% (P < 0.05) with clenbuterol-treatment (1 x 10(-6) mol.L-1), and the enhanced effect of 3H-leucine incorporation into hepatocyte was antagonized by propranolol (1 x 10(-6) mol.L-1. The level of 3H-leucine incorporation of rat hepatocyte was not influenced by propranolol alone. IGF-I production of rat hepatocyte might be affected by clenbuterol. IGF-I concentration of culture medium was increased by 39.46% with clenbuterol (1 x 10(-6) mol.L-1), but no significant difference was found compared with the control (P > 0.05). Moreover, G6PDH activity of rat hepatocyte was significantly decreased by 43.36% (P < 0.05) with clenbuterol treatment (1 x 10(-6) mol.L-1), and the declined effect of clenbuterol was antagonized by propranolol. G6PDH activity of rat hepatocyte was not affected on condition that propranolol was administered alone (P > 0.05).

CONCLUSIONIt is suggested that clenbuterol may regulate nitrogen and fat metabolism by means of increasing nitrogen retention and protein synthesis, and decreasing G6PDH activity of rat hepatocyte for pharmacological effects.

Adrenergic beta-2 Receptor Agonists ; Animals ; Cells, Cultured ; Clenbuterol ; pharmacology ; Glucosephosphate Dehydrogenase ; metabolism ; Hepatocytes ; drug effects ; enzymology ; metabolism ; Nitrogen ; metabolism ; Rats ; Rats, Sprague-Dawley