The effect of dobutamine on rat cardiac cyclic AMP, phosphorylase a and force of contraction.

Dobutamine produced a dose-dependent increase in cardiac cyclic AMP, % phosphorylase a and contractile force in the isolated perfused rat heart. Cyclic AMP increased prior to the increase in % phosphorylase a and prior to or concomitant with the increase in force. Similar results were obtained with isoproterenol except that the effects of isoproterenol occurred slightly earlier. The efficacy of both amines was approximately the same but dobutamine was was about 1/45 as potent as isoproterenol.