The inotropic action of epinephrine does not correlate with phosphorylase activation, which only occurs after cardiac activity is significantly increased.
SummaryThe effects of epinephrine on inotropic action and on phosphorylase activation have been examined in perfused rat hearts and in dog hearts in situ. Small doses of epinephrine caused significant increases in contractile force without augmenting phosphorylase a levels. It is concluded that activation of phosphorylase does not correlate with the inotropic action of the drug, but occurs only after cardiac activity is significantly increased.
Drummond et al. (Thu,) studied this question.