Adenosine receptor

From Academic Kids

The adenosine receptors are a class of G-protein coupled receptors with adenosine as endogenous ligand.

Contents

A1 adenosine receptor

A2A adenosine receptor

The A1 and A2a receptors of endogenous adenosine are believed to play a role in regulating myocardial oxygen consumption, and coronary blood flow[1]. Stimulation of the A1 receptor has a myocardial depressant effect; by decreasing the conduction of electrical impulses, and suppressing pacemaker cell function resulting in a decrease in heart rate. This makes adenosine [as Adenocard] as useful medication for treating and diagnosing tachyarrhythmias, or excessively fast heart rates. This effect on the A1 receptor also explains why there is a brief moment of cardiac standstill when adenosine is administered as a rapid IV push during cardiac resuscitation. The rapid infusion causes a momentary myocardial stunning effect. In comparison, the A2a receptor is responsible for regulating myocardial blood flow by vasodilating the coronary arteries. Increased blood flow to the myocardium increases the amount of oxygen available to the heart. In normal physiological states; both of these receptors serve as protective mechanisms. However, in altered cardiac function such as hypoperfusion caused by hypotension, heart attack or cardiac arrest caused by nonperfusing bradycardias, Adenosine has a negative effect of physiological functioning by preventing necessary compensatory increases in heart rate and blood pressure that attempt to maintain cerebral perfusion. Recent research on adenosine receptor function, and adenosine receptor antagonists such as theophylline has lead to several randomized controlled trials using these receptor antagonists to treat bradyasystolic arrest[1-8]. The primary researchers, TJ Mader et al, at Tuffs University School of Medicine have reported some promising results.


The author of this segment has no affiliation with any of the research, or researchers mentioned and is currently drafting a review of the literature on the use of theophylline in bradyasystolic arrest as part of graduate coursework. 


References / Resources for more information

1. Mader TJ, Bertolet BD, Ornato JP, Gutterman JM. Aminophylline in the treatment of atropine resistant bradyasystole. Resuscitation. 2000;47:105-112.

2. Burton JH, Mass M, Menegazzi JJ, Yealy DM. Aminophylline as an adjunct to standard advanced cardiac life support in prolongued cardiac arrest. Ann Emerg Med. 1997;30:154-160.

3. Khoury MY, Moukarbel GV, Obeid MY, Alam SE. Effects of aminophylline on conplete atrioventricular black with ventricular asystole following blunt chest trauma. Injury, Int J care Injured. 2001;32:335-338. [case report].

4. Mader TJ, Smithline HA, Durkin L, Scriver G. A randominzed controlled trial of intravenous aminophylline for atropine resistant out-of-hospital asystolic cardiac arrest. Acad Emerg Med. 2003;10:192-197.

5. Mader TJ, Smithline Ha, Gibson P. Aminophylline in undifferentiated out-of-hospital asytolic cardiac arrest. Resuscitation. 1999;41:39-45.

6. Mader TJ, Gibson P. Adenosine receptor antagonism in refractory asystolic cardiac arrest: results of a human pilot study. Resuscitation. 1997;35:3-7.

7. Perouansky M, Shamir M, Hershkowitz E, Donchin Y. Successful resuscitation using aminophylline in refractory cardiac arrest with asystole. Resuscitation. 1998;38:39-41. [case reports].

8. Viskin S, Belhassen B, Roth, A, et al. Aminophylline for bradysystolic cardiac arrest refractory to atropine and epinephrine. Ann Intern Med. 1993;118:279-281.

A2B adenosine receptor

A3 adenosine receptor

Template:Biochem-stub

It has been shown in studies to inhibit some specific signal pathways of adenosine. It allows for the inhibition of growth in human melanoma cells.

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