Inhibition of Ca(2+)-regulated exocytosis by levetiracetam, a ligand for SV2A, in antral mucous cells of guinea pigs.
Levtiracetam (Lev), an inhibitor of SV2A (synaptic vesicle protein A2), affected the ATP-dependent priming of Ca(2+)-regulated exocytosis in antral mucous cells of guinea pig. In antral mucous cells, the Ca(2+)-regulated exocytosis, which is activated by acetylcholine (ACh), consists of an initial peak that declines rapidly (initial phase) followed by a second slower decline (late phase). Dinitrophenol (DNP), which depletes ATP, inhibits the ATP-dependent priming. DNP abolished the initial phase by reducing the number of primed granules, Lev decreased the frequency of initial phase, but not in the presence of DNP. Moreover, 8-bromoguanosine 3'5'-cyclic monophosphate (8BrcGMP) accelerates the ATP-dependent priming. 8BrcGMP enhances the frequency of initial phase by increasing the number of primed granule. Lev added prior to 8BrcGMP addition decreased the frequency of initial phase, but Lev added after 8BrcGMP addition did not. Thus, Lev affected the granules in the process of priming, but it did not affect the granules already primed. Lev did not affect [Ca(2+)]i in unstimulated or ACh-stimulated antral mucous cells. Immunohistochemistry and western blotting demonstrated that SV2A exists in antral mucous cells. The results suggest that SV2A plays an essential role in maintaining the process of ATP-dependent priming in antral mucous cells. In conclusion, Lev decreases the frequency of Ca(2+)-regulated exocytosis the number of primed granules by inhibiting SV2A functions, leading to a decrease in antral mucous cells.
Nakahari Project of Central Research Laboratory, Osaka Medical College, Takatsuki 569-8686, Japan; Laboratory of Pharmacotherapy, Osaka University of Pharmaceutical Sciences, Takatsuki 569-1094, Japan.
Saeko
S
Harada
Saori
S
Tanaka
Yuko
Y
Takahashi
Hitoshi
H
Matsumura
Chikao
C
Shimamoto
Takashi
T
Nakano
Hiroko
H
Kuwabara
Yukinori
Y
Sawabe
Takashi
T
Nakahari
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects*; D005753:Gastric Mucosa / Q000166:cytology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006168:Guinea Pigs; D000077287:Levetiracetam; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D010889:Piracetam / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects
D008024:Ligands; D008562:Membrane Glycoproteins; D000077287:Levetiracetam; D000255:Adenosine Triphosphate; D000109:Acetylcholine; D002118:Calcium; D010889:Piracetam
ATP-dependent priming; Ca(2+)-regulated exocytosis; Gastric mucin; Levetiracetam; SV2A