cGMP modulation of ACh-stimulated exocytosis in guinea pig antral mucous cells.
In guinea pig antral mucous cells, ACh stimulates the Ca(2+)-regulated exocytosis, which has a characteristics feature: an initial transient phase followed by a sustained phase. The effects of cGMP on ACh-stimulated exocytosis were studied in guinea pig antral mucous cells using video microscopy. cGMP enhanced the frequency of ACh-stimulated exocytotic events, whereas cGMP alone did not induce any exocytotic events under the ACh-unstimulated condition. cGMP did not stimulate either Ca(2+) mobilization or cAMP accumulation. The Ca(2+) dose-response studies demonstrated that cGMP shifted the dose-response curve upward with no shift to the lower concentration. This indicates that cGMP increased maximal responsiveness of the Ca(2+)-regulated exocytosis, but not the Ca(2+) sensitivity. Moreover, under a condition of ATP depletion by dinitrophenol (DNP) or anoxia (N(2) bubbling), ACh evoked only a sustained phase in exocytotic events with no initial transient phase. However, ACh evoked an initial transient phase followed by a sustained phase with addition of cGMP before ATP depletion, whereas only a sustained phase was evoked in a case of cGMP addition after ATP depletion. Thus cGMP-induced enhancement in ACh-stimulated exocytotic events requires ATP, suggesting that cGMP modulates ATP-dependent priming of Ca(2+)-regulated exocytosis in antral mucous cells. In conclusion, cGMP increases the number of primed granules via acceleration of the ATP-dependent priming, which enhances the Ca(2+)-regulated exocytosis stimulated by ACh.
Saad
Adel H
AH
Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Japan.
Shimamoto
Chikao
C
Nakahari
Takashi
T
Fujiwara
Shoko
S
Katsu
Ken-ichi
K
Marunaka
Yoshinori
Y
D000109:Acetylcholine / Q000008:administration & dosage*; D000818:Animals; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D008297:Male; D009077:Mucins / Q000378:metabolism*; D011706:Pyloric Antrum / Q000187:drug effects / Q000378:metabolism*
D004338:Drug Combinations; D009077:Mucins; D006152:Cyclic GMP; D000109:Acetylcholine