[Intracellular Ca2+ response induced by acetylcholine in the submucosal nasal gland acinar cells of guinea pigs].
We examined intracellular Ca2+ responses of nasal gland acinar cells in order to clarify cellular responses and molecular events with regard to the regulatory mechanism of nasal secretion. The acinar cells of the serous gland, in the guinea-pig nasal septum, were obtained by meticulous and selective dissection with minimal contamination of epithelial lining cells followed by collagenase treatment. The dispersed acini were incubated in an oxygenated solution supplemented with fura -2 acetoxymethyl ester and the intracellular Ca2+ concentration ([Ca2+]i) was measured using fluorescence ratio imaging microscopy. The application of acetylcholine (ACh) to the nasal gland acinar cells induced an initially rapid increase in [Ca2+]i followed by a sustained plateau. The increase in [Ca2+]i induced by ACh was concentration-dependent and ranged from 10(-8) to 10(-5) M. The intracellular Ca2+ response was completely inhibited by atropine, indicating the presence of muscarinic cholinergic receptors. Removal of external Ca2+ with addition of EGTA resulted in a transient increase without a sustained phase. The sustained phase of the [Ca2+]i increase induced by ACh was inhibited by Ni2+, but not by nifedipine. The initial phase seems to be due to mobilization from cytosolic Ca2+ stores while the subsequent sustained phase is dependent on the influx of external Ca2+ ions sensitive to Ni2+. We have demonstrated that increasing the Ca2+ gradient by elevating external Ca2+ accelerates Ca2+ entry, and that depolarization of cells due to elevated external K+ attenuates Ca2+ entry. These findings suggest that the Ca2+ entry process in nasal gland acinar cells is dependent on the electrochemical gradient across the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
Ishigaki
M
M
Department of Otolaryngology, Tohoku University School of Medicine, Sendai.
Ikeda
K
K
Sunose
H
H
Suzuki
M
M
Takasaka
T
T
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006168:Guinea Pigs; D009297:Nasal Mucosa / Q000166:cytology* / Q000378:metabolism*
D000109:Acetylcholine; D002118:Calcium