[Cl-]i modulation of Ca2+-regulated exocytosis in ACh-stimulated antral mucous cells of guinea pig.
The effects of intracellular Cl- concentration ([Cl-]i) on acetylcholine (ACh)-stimulated exocytosis were studied in guinea pig antral mucous cells by video microscopy. ACh activated Ca2+-regulated exocytosis (an initial phase followed by a sustained phase). Bumetanide (20 microM) or a Cl- -free (NO3-) solution enhanced it; in contrast, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, a Cl- channel blocker) decreased it and eliminated the enhancement induced by bumetanide or NO3- solution. ACh and Ca2+ dose-response studies demonstrated that NO3- solution does not shift their dose-response curves, and ATP depletion studies by dinitrophenol or anoxia demonstrated that exposure of NO3- solution prior to ATP depletion induced an enhanced initial phase followed by a sustained phase, whereas exposure of NO3- solution after ATP depletion induced only a sustained phase. Intracellular Ca2+ concentration ([Ca2+]i) measurements showed that bumetanide and NO3- solution enhanced the ACh-stimulated [Ca2+]i increase. Measurements of [Cl-]i revealed that ACh decreases [Cl-]i and that bumetanide and NO3- solution decreased [Cl-]i and enhanced the ACh-evoked [Cl-]i decrease; in contrast, NPPB increased [Cl-]i and inhibited the [Cl-]i decrease induced by ACh, bumetanide, or NO3- solution. These suggest that [Cl-]i modulates [Ca2+]i increase and ATP-dependent priming. In conclusion, a decrease in [Cl-]i accelerates ATP-dependent priming and [Ca2+]i increase, which enhance Ca2+-regulated exocytosis in ACh-stimulated antral mucous cells.
Central Research Laboratory (Nakahari Project), Osaka Medical College, Takatsuki 569-8686, Japan.
Chikao
C
Shimamoto
Eiji
E
Umegaki
Ken-ichi
K
Katsu
Masumi
M
Kato
Shoko
S
Fujiwara
Takahiro
T
Kubota
Takashi
T
Nakahari
D000109:Acetylcholine / Q000502:physiology*; D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D002712:Chlorides / Q000494:pharmacology / Q000502:physiology*; D004140:Dinitrophenols / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects* / Q000502:physiology; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D000860:Hypoxia / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D009566:Nitrates / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology; D011706:Pyloric Antrum / Q000187:drug effects / Q000378:metabolism*
D018118:Chloride Channels; D002712:Chlorides; D004140:Dinitrophenols; D009566:Nitrates; D009579:Nitrobenzoates; D002034:Bumetanide; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D004533:Egtazic Acid; D015759:Ionomycin; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D000109:Acetylcholine; D002118:Calcium