Fig. 9. (A ) Summarized data for the effect of phorbol myristate acetate (PMA) on isoproterenol-stimulated cyclic adenosine monophosphate (cAMP) production in rat ventricular myocytes. (B ) Summarized data for the effect of bisindolylmaleimide I (Bis) on isoproterenol (Iso)-stimulated cAMP production. (C ) Summarized data for the effect of Gö 6976 on isoproterenol-stimulated cAMP production. Results are expressed as picomoles per milligram protein. *  P < 0.05 compared with isoproterenol. n = 8 hearts.