Interaction between adenosine and catecholamines on cyclic AMP accumulation in guinea pig ventricular myocardium

Abstract

Adenosine stimulated cyclic AMP accumulation in guinea pig ventricular slice preparations Stimulation produced by adenosine and isoproterenol combined was essentially the sum of the two individual responses. In contrast, the response produced by adenosine and epinephrine or adenosine and norepinephrine was lower than that produced by the nucleoside alone. In the absence or presence of adenosine, propranolol decreased epinephrine- or norepinephrine-mediated accumulation of cyclic AMP below control levels, whereas phentolamine increased these responses. Methoxamine reduced cyclic AMP accumulation mediated by isoproterenol or adenosine. The results are interpreted to indicate that alpha and beta adrenergic agents have opposing effects on cyclic AMP formation in this preparation, alpha receptor stimulation acting to decrease cyclic AMP levels. The effect of alpha receptor activation was particularly pronounced when cyclic AMP levels were elevated by adenosine.