| 词条 | Beta-adrenergic agonist |
| 释义 |
| Name = Beta adrenergic receptor agonists | Image = Salbutamol.svg | Alt = Albuterol | Use = Bradycardia, Asthma, heart failure, etc. | Caption = Skeletal structure formula of salbutamol (albuterol) — a widely used medication to treat asthma attacks | Biological_target = Adrenergic receptors (β subtype) | ATC_prefix = R03 | MeshID = D000318 }}Beta adrenergic agonists or beta agonists are medications that relax muscles of the airways, which widen the airways and result in easier breathing.[1] They are a class of sympathomimetic agents which act upon the beta adrenoceptors.[2] In general, pure beta-adrenergic agonists have the opposite function of beta blockers. Beta adrenoreceptor agonist ligands mimic the action of epinephrine and norepinephrine signaling in the heart, lungs, and smooth muscle tissue, with epinephrine expressing the highest affinity. The activation of β1, β2 and β3 activates the enzyme, adenylate cyclase. This, in turn, leads to the activation of the secondary messenger cyclic adenosine monophosphate (cAMP), cAMP then activates protein kinase A (PKA) which phosphorylates target proteins, ultimately inducing smooth muscle relaxation and contraction of the cardiac tissue.[3] FunctionActivation of β1 receptors induces positive inotropic, chronotropic output of the cardiac muscle, leading to increased heart rate and blood pressure, secretion of ghrelin from the stomach, and renin release from the kidneys.[4] Activation of β2 receptors induces smooth muscle relaxation in the lungs, gastrointestinal tract, uterus, and various blood vessels. Increased heart rate and heart muscle contraction are associated with the β1 receptors; however, β2 cause vasodilation in the myocardium. β3 receptors are mainly located in adipose tissue.[5] Activation of the β3 receptors induces the metabolism of lipids.[6] Medical usesIndications of administration for β agonists include:
Side effectsAlthough minor compared to those of epinephrine, beta agonists usually have mild to moderate adverse effects, which include anxiety, hypertension, increased heart rate, and insomnia. Other side effects include headaches and essential tremor. Hypoglycemia was also reported due to increased secretion of insulin in the body from activation of β2 receptors. In 2013, zilpaterol, a β agonist sold by Merck, was temporarily withdrawn due to signs of sickness in some cattle that were fed the drug.[8] Receptor selectivityMost agonists of the beta receptors are selective for one or more beta-adrenoreceptors. For example, patients with low heart rate are given beta agonist treatments that are more "cardio-selective" such as dobutamine, which increases the force of contraction of the heart muscle. Patients who are suffering from a chronic inflammatory lung diseases such as asthma or COPD are treated with salbutamol (albuterol), which mainly induces smooth muscle relaxation in the lungs and less contraction of the heart.[9] β3 agonists are currently in clinical research and are thought to increase the breakdown of lipids in obese patients.[10] β1 agonists{{Main|Beta-1_adrenergic_receptor#Agonists}}β1 agonists stimulate adenylyl cyclase activity and opening of calcium channel (cardiac stimulants; used to treat cardiogenic shock, acute heart failure, bradyarrhythmias). Selected examples are:
β2 agonists{{Main|Beta2-adrenergic agonist|l1=Beta2-adrenergic agonist}}β2 agonists stimulate adenylyl cyclase activity and closing of calcium channel (smooth muscle relaxants; used to treat asthma and COPD). Selected examples are: {{div col|colwidth=30em}}
Undetermined/unsortedThese agents are also listed as agonists by MeSH.[11] {{div col|colwidth=30em}}
See also
References1. ^{{cite web|title=WHAT ARE BETA-AGONISTS?|url=http://www.thoracic.org/clinical/copd-guidelines/for-patients/what-kind-of-medications-are-there-for-copd/what-are-beta-agonists.php|website=Thoracic.org|publisher=American Thoracic Society|accessdate=17 October 2014}} {{Adrenergic agonists}}{{Receptor agonists and antagonists}}2. ^{{MeshName|Adrenergic+beta-Agonists}} 3. ^{{cite news|last=Delbruck|first=Max|pmid=12439640|title=The beta-adrenergic receptors}} 4. ^{{cite news|last=Yoo|first=B.|pmid=19633206|title=Beta1-adrenergic receptors stimulate cardiac contractility and CaMKII activation in vivo and enhance cardiac dysfunction following myocardial infarction|display-authors=etal}} 5. ^{{cite news|last=Johnson|first=M.|pmid=16387578|title=Molecular mechanisms of beta(2)-adrenergic receptor function, response, and regulation}} 6. ^{{cite news|last=Lowell|first=B.B.|last2=Flier|first2=J.S.|pmid=9046964|title=Brown adipose tissue, beta 3-adrenergic receptors, and obesity|journal=Annu. Rev. Med.|year=1997|volume=48|pages=307–16}} 7. ^https://www.fda.gov/Drugs/DrugSafety/ucm243539.htm 8. ^{{cite web|url=https://news.yahoo.com/exclusive-fda-says-working-merck-usda-cattle-drug-160545615.html |title=Archived copy |accessdate=2013-08-16 |deadurl=yes |archiveurl=https://web.archive.org/web/20130827081850/http://news.yahoo.com/exclusive-fda-says-working-merck-usda-cattle-drug-160545615.html |archivedate=2013-08-27 |df= }} 9. ^{{cite news|last=Pias|first=M.T.|url=http://www.uky.edu/~mtp/OBI836AR.html|title=The Pharmacology of Adrenergic Receptors}} 10. ^{{cite news|last=Meyers|first=D.S.|author2=Skwish, S. |author3=Dickinson, K.E. |author4=Kienzle, B. |author5=Arbeeny, C.M. |pmid=9024225|title=Beta 3-adrenergic receptor-mediated lipolysis and oxygen consumption in brown adipocytes from cynomolgus monkeys|journal=J. Clin. Endocrinol. Metab.|date=Feb 1997|volume=82|number=2|pages=395–401}} 11. ^{{MeshPharmaList|82000318}} 1 : Beta-adrenergic agonists |
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