Influence of cyclic 3',5'-adenosine monophosphate and adenosine on vascular reactivity.

cAMP, 5'-AMP and adenosine in doses of 1, 2 and 5 mg/kg i.v. in rats diminish vascular resistance in the hind limbs in vivo and in isolated limbs perfused with nutrient fluid containing adrenaline (A) (10(-3) M), slowing action of the heart and lowering blood pressure. After administration of cAMP, 5'-AMP and adenosine (5 mg/kg), vasoconstricting action of noradrenaline (NA) and A was depressed, and the vasodilating action of isoprenaline (I) was enhanced. The changes in blood pressure observed after administration of the tested adenosine compounds were not blocked by phentolamine, but after I were blocked by propranolol. cAMP, 5'-AMP and adenosine had no influence on the drop in blood pressure elicited by acetylcholine. The results indicate that cAMP, 5'-AMP and adenosine increase reactivity of beta-receptors of the sympathetic system in the blood vessels and modify the action of catecholamines on blood vessels.