Okadaic acid inhibits amylase exocytosis from parotid acini stimulated by cyclic AMP.
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.
Takuma
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T
Department of Oral Biochemistry, School of Dentistry, Higashi Nippon Gakuen University, Hokkaido, Japan.
Ichida
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T
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
D004988:Ethers, Cyclic; D012503:Saponins; D019319:Okadaic Acid; D000242:Cyclic AMP; D000681:Amylases; D007545:Isoproterenol