title: Okadaic acid inhibits amylase exocytosis from parotid acini stimulated by cyclic AMP.
abstract: To evaluate the role of protein phosphorylation in amylase exocytosis, we studied the effects of okadaic acid, a potent inhibitor of protein phosphatase types 1 and 2A, on amylase release and protein phosphorylation in rat parotid acini. Although okadaic acid by itself weakly stimulated amylase release, it did not potentiate amylase release stimulated by half-maximum doses of isoproterenol or cAMP, and markedly inhibited their maximum effects. Okadaic acid dose-dependently increased cAMP-independent phosphorylation of some proteins and enhanced cAMP-dependent phosphorylation of 21- and 26-kDa proteins. These results indicate that increase in protein phosphorylation does not necessarily enhance the exocytosis of amylase from parotid acini.
authors.affiliation: Department of Oral Biochemistry, School of Dentistry, Higashi Nippon Gakuen University, Hokkaido, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Takuma
authors.forename: T
authors.initials: T
authors.lastname: Ichida
mesh_terms: D000681:Amylases / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004988:Ethers, Cyclic / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D019319:Okadaic Acid; D010306:Parotid Gland / Q000187:drug effects* / Q000201:enzymology; D010766:Phosphorylation; D051381:Rats; D012503:Saponins / Q000494:pharmacology
chemical_list: D004988:Ethers, Cyclic; D012503:Saponins; D019319:Okadaic Acid; D000242:Cyclic AMP; D000681:Amylases; D007545:Isoproterenol