Evidence for a Role of Cyclic AMP and Endothelium in Rat Aortic Relaxa- tion Induced by R-PIA

It is known that vasodilator effects of adenosine are mediated by A2 receptors in various animal species. Nevertheless, in several blood vessels there is evidence for vasodilator responses to some adenosine analogues, which are resistant to the antagonists of the different adenosine receptor subtypes, suggesting that they are not mediated by any of the known adenosine receptors. There are contradictory reports about the effects produced by adenosine and its analogues on aortic vasodilation. The results obtained in the present study dealing with rat aortic rings and the relaxant effects induced by the selective adenosine A1 receptor agonist N-R-phenylisopropyladenosine (R-PIA) provide evidence that cyclic AMP and the presence of endothelium are possibly involved in rat aortic relaxation induced by this adenosine analogue.