Cardiovascular actions of substituted adenosine analogues.

1. The effects of adenosine on systemic blood pressure, coronary blood flow and cardiac contractility and rate were studied in anaesthetized open-thorax dogs.2. The potency and duration of action of substituted adenosine analogues were compared with that of adenosine.3. With the exception of 2-chloroadenosine, in which coronary dilator activity was enhanced, substitution in the 2-position of the adenosine molecule reduced activity.4. In all cases 2-substitution prolonged the duration of the coronary dilator activity of adenosine.5. N(6)-Methylation of adenosine and 2-chloroadenosine reduced their coronary dilator activities, but had no effect on the duration of the response.6. Comparison of the coronary dilator potencies and hypotensive activities of 2-ethylaminoadenosine and 2-methoxyadenosine indicates that these analogues have some specificity for the coronary bed.