Adenosine relaxes the aorta by interacting with an A2 receptor and an intracellular site

Eur J Pharmacol. 1983 Dec 9;96(1-2):61-9. doi: 10.1016/0014-2999(83)90529-0.


The purpose of this study was to determine whether the adenosine receptor that mediates relaxation of the noradrenaline-contracted guinea-pig aorta is of the A1 or A2 subtype. 5'-N-ethylcarboxamide adenosine (NECA) and 5'-N-cyclopropylcarboxamide adenosine (NCPCA) were about 100 times more potent as relaxants of the aorta than L-N6-phenylisopropyladenosine (L-PIA) and N6-cyclohexyladenosine. L-PIA was 3 times more potent than D-PIA. These relaxations were not altered by the purine transport inhibitor dipyridamole, but were attenuated by the cell surface adenosine receptor antagonist 8-phenyltheophylline. Adenosine and 2-chloroadenosine differed from NECA and NCPCA since they evoked greater maximal relaxations and their submaximal responses were less sensitive to blockade by 8-phenyltheophylline. These differences were abolished by dipyridamole which indicates that they were due to an intracellular action of adenosine and 2-chloroadenosine. The intracellular 'P-site' agonist, 9-beta-D-xylofuranosyladenine evoked small relaxations that were attenuated by dipyridamole but were unaffected by 8-phenyltheophylline. These results indicate that adenosine can relax the aorta via interactions with a cell surface A2 receptor and with an intracellular site.

MeSH terms

  • Adenosine / analogs & derivatives
  • Adenosine / pharmacology*
  • Animals
  • Aorta / drug effects
  • Dipyridamole / pharmacology
  • Drug Interactions
  • Female
  • Guinea Pigs
  • In Vitro Techniques
  • Male
  • Muscle Contraction / drug effects*
  • Muscle Relaxation / drug effects*
  • Muscle, Smooth, Vascular / drug effects*
  • Norepinephrine / pharmacology
  • Receptors, Cell Surface / drug effects*
  • Receptors, Purinergic
  • Sodium Nitrite / pharmacology
  • Theophylline / analogs & derivatives
  • Theophylline / pharmacology


  • Receptors, Cell Surface
  • Receptors, Purinergic
  • Dipyridamole
  • Theophylline
  • 8-phenyltheophylline
  • Adenosine
  • Sodium Nitrite
  • Norepinephrine