Alterations in myocardial and plasma cyclic adenosine monophosphate in experimental myocardial ischemia

Alterations in myocardial and plasma cyclic adenosine monophosphate (cyclic AMP) levels were studied following clamping of the aorta or coronary artery occlusion in 30 dogs. Plasma cyclic AMP levels increased markedly after thoracotomy but returned to control levels 2 hr later. Complete arrest of aortic flow (clamping) induced a significant early increase in the myocardial cyclic AMP levels of all animals studied. No increase was noted following pretreatment with propranolol or sham occlusion. Localized coronary occlusion tended to increase plasma cAMP levels in anesthetized animals and also in concious dogs. The present study suggests that adrenergically mediated changes in tissue and plasma cyclic AMP content are early manifestations of both generalized and local myocardial ischemia and tend to reflect the magnitude of the insult.