title: A PKG inhibitor increases Ca(2+)-regulated exocytosis in guinea pig antral mucous cells: cAMP accumulation via PDE2A inhibition.
abstract: In antral mucous cells, acetylcholine (ACh, 1 μM) activates Ca(2+)-regulated exocytosis, consisting of an initial peak that declines rapidly (initial transient phase) followed by a second slower decline (late phase) lasting during ACh stimulation. The addition of 8-bromo-cGMP (8-BrcGMP) enhanced the initial phase, which was inhibited by the protein kinase G (PKG) inhibitor guanosine 3',5'-cyclic monophosphorothoiate, β-phenyl-1,N(2)-etheno-8-bromo, Rp-isomer, sodium salt (Rp-8-BrPETcGMPS, 100 nM). However, Rp-8-BrPETcGMPS produced a delayed, but transient, increase in the exocytotic frequency during the late phase that was abolished by a protein kinase A (PKA) inhibitor (PKI-amide), suggesting that Rp-8-BrPETcGMPS accumulates cAMP. The cGMP-dependent phosphodiesterase 2 (PDE2), which degrades cAMP, may exist in antral mucous cells. The PDE2 inhibitor BAY-60-7550 (250 nM) mimicked the effect of Rp-8-BrPETcGMPS on ACh-stimulated exocytosis. Measurement of the cGMP and cAMP contents in antral mucosae revealed that ACh stimulates the accumulation of cGMP and that BAY-60-7550 accumulates cAMP similarly to Rp-8-BrPETcGMPS during ACh stimulation. Analyses of Western blot and immunohistochemistry demonstrated that PDE2A exists in antral mucous cells. In conclusion, Rp-8-BrPETcGMPS accumulates cAMP by inhibiting PDE2 in ACh-stimulated antral mucous cells, leading to the delayed, but transient, increase in the frequency of Ca(2+)-regulated exocytosis. PDE2 may prevent antral mucous cells from excessive mucin secretion caused by the cAMP accumulation.
authors: Nakahari Project of Central Research Laboratory, Osaka Medical College, Takatsuki, Japan.
authors: Saori
authors: S
authors: Tanaka
authors: Rina
authors: R
authors: Tanaka
authors: Saeko
authors: S
authors: Harada
authors: Yuka
authors: Y
authors: Kohda
authors: Hitoshi
authors: H
authors: Matsumura
authors: Chikao
authors: C
authors: Shimamoto
authors: Yukinori
authors: Y
authors: Sawabe
authors: Yoshinori
authors: Y
authors: Marunaka
authors: Hiroko
authors: H
authors: Kuwabara
authors: Yuko
authors: Y
authors: Takahashi
authors: Shigenori
authors: S
authors: Ito
authors: Takashi
authors: T
authors: Nakahari
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology*; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2 / Q000037:antagonists & inhibitors; D015232:Dinoprostone / Q000378:metabolism; D005089:Exocytosis / Q000187:drug effects*; D005753:Gastric Mucosa / Q000187:drug effects; D006168:Guinea Pigs; D008297:Male; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011706:Pyloric Antrum / Q000187:drug effects / Q000502:physiology*
chemical_list: D047428:Protein Kinase Inhibitors; C582074:beta-phenyl-1,N2-etheno-8-bromoguanosine 3',5'-cyclic monophosphorothoiate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2; D006152:Cyclic GMP; D015232:Dinoprostone; D000109:Acetylcholine; D002118:Calcium
keywords: acetylcholine; adenosine 3′,5′-cyclic monophosphate; gastric; guanosine 3′,5′-cyclic monophosphate; mucin secretion