Comparison of endothelium-related responses to nucleotides of dog and monkey cerebral arteries.

We compared mechanical responses to uridine-5'triphosphate (UTP) and 2-(methylthio)adenosine-5'diphosphate (2MeSADP) of cerebral arteries isolated from dogs and monkeys. In the dog, UTP induced endothelium-independent contraction, whereas 2MeSADP induced endothelium-dependent relaxation that was abolished by N(G)-nitro-L-arginine (L-NA). In the monkey, both UTP and 2MeSADP induced endothelium-dependent relaxation. L-NA largely inhibited the UTP-induced relaxation whereas it partially inhibited the 2MeSADP-induced relaxation, and both remaining relaxations were abolished by charybdotoxin plus apamin. In conclusion, dog and monkey cerebral arteries respond differentially to UTP and similarly to 2MeSADP; however, involvement of endothelium-derived relaxing factor in the endothelium-dependent relaxation by 2MeSADP is quite different between the two species.