Cardiovascular pharmacology of purines. Clin. Sci

1, This review focuscs on the extracellular actions of ATP and adenosine, and in particular their role in cardiovascular regulation. 2, ATP serves as a co-transmitter within the sympa thetic nervous system, and is also released from endothelium and aggregating thrombocytes. ATP acts on P2x purinoceptors on vascular smooth muscle cells to induce vasoconstriction. Stimulation of P2y purinoceptors on endothelial cells releases endothelium-derived relaxing factors and causes vasodilatation. This dual action of ATP may have pathophysiological importance by inducing vasospasm at sites of impaired endothelial function and thrombus forma lion. 3. Adenosine is generated by enzymic degradatio