Activation of cAMP-dependent protein kinase without a corresponding increase in phosphorylase activity.

The effect of prostaglandin E1(PGE1) and epinephrine on glycogen metabolism has been investigated in the perfused rat heart. Both agents produced increases in cAMP and the cAMP-dependent protein kinase activity ratio. When dosages were adjusted to give equal increases in the protein kinase activity ratio from a basal value of 0.15 to as high as 0.40, only epinephrine caused a significant increase in phosphorylase activity. When used together, PGE1 did not effect the ability of epinephrine to increase phosphorylase activity.