Evidence against the adenosine-catecholamine antagonism under in vivo conditions

Experiments were carried out in anaesthetized, thoracotomized dogs. The dose dependent positive inotropic and chronotropic effects of intracoronary (i.cor.) infusions or bolus injections of isoproterenol (ISO) were neither antagonized by adenosine (0.46, 1.0, and 2.91 x 10(-5) mol/l) nor by the adenosine analogue N6-phenylisopropyl-adenosine (PIA, 3.23 x 10(-7) mol/l). The results indicate, that adenosine and PIA do not have any antagonistic effects on isoproterenol induced positive inotropy and chronotropy in the intact dog heart. Consequently it can be assumed that an adenosine-catecholamine antagonism is of no physiological relevance.