The role of cyclic AMP in the regulation of exocytosis in the rat parotid gland: evidence obtained with the isoproterenol analog PI-39

J Cyclic Nucleotide Res. 1982;8(4):225-34.


The isoproterenol analog, PI-39, induced a dose-dependent release of alpha-amylase from rat parotid minces in vitro. This effect was blocked by propranolol, a beta-adrenergic antagonist. PI-39 alone had no effect on parotid cyclic AMP levels or on protein kinase activation as assessed by the activity ratios method. However, PI-39 produced a dose-dependent increase in these parameters when a phosphodiesterase inhibitor was added to tissue minces simultaneously with the isoproterenol analog. Both isoproterenol and PI-39 altered the phosphorylation state of at least three specific endogenous phosphoproteins in (32P)-Pi prelabelled minces. The presence of a phosphodiesterase inhibitor was not required to demonstrate the effects of PI-39 on protein phosphorylation. Studies of endogenous protein phosphorylation in parotid broken cell preparations demonstrated that the phosphorylation of at least two of the PI-39 and isoproterenol-affected phosphoproteins are influenced by cyclic AMP. This study demonstrates that, under certain conditions, it is possible to activate a cyclic AMP-regulated biological process without elevating the total cellular cyclic AMP concentration or the protein kinase activity ratio.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amylases / metabolism
  • Animals
  • Cyclic AMP / physiology*
  • Exocytosis*
  • In Vitro Techniques
  • Octopamine / analogs & derivatives*
  • Octopamine / pharmacology
  • Parotid Gland / drug effects
  • Parotid Gland / enzymology
  • Parotid Gland / physiology*
  • Rats


  • Octopamine
  • deterenol
  • Cyclic AMP
  • Amylases