title: The role of cyclic AMP in the regulation of exocytosis in the rat parotid gland: evidence obtained with the isoproterenol analog PI-39.
abstract: 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.
mesh_terms: D000681:Amylases / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000502:physiology*; D005089:Exocytosis; D066298:In Vitro Techniques; D009655:Octopamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010306:Parotid Gland / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D051381:Rats
chemical_list: D009655:Octopamine; C001416:deterenol; D000242:Cyclic AMP; D000681:Amylases