Effect of the uncharged imidazolium moiety in adenine on endothelium-independent relaxation in the contracted thoracic aorta of Sprague-Dawley rats.

Adenine had a concentration-dependent relaxation action on the phenylephrine-contracted aorta ring, with an EC(50) value of 0.40±0.12 mM. This effect was also observed in the endothelium-denuded aorta. Among the adenine analogues, N-methyladenine and benzimidazole still evoked an apparent relaxation effect, while 1-, 3- or 7-methyladenine and imidazole were no longer vasodilators. These findings demonstrate that the imino group from the uncharged imidazolium moiety in adenine played a key role in the relaxation of the contracted aorta.