title: Effects of Ca2+ removal and of tetraethylammonium on membrane currents induced by carbachol in isolated cells from the rat parotid gland.
abstract: In freshly dispersed rat parotid acinar cells, 10 microM carbachol increased outward currents at 0 mV and also inward currents at -70 mV recorded with the wholecell clamp method using patch pipettes containing 1 mM EGTA. When EGTA in the pipette was increased to 2.4 mM, carbachol increased only outward currents and a further increase of EGTA to 4 mM blocked the carbachol response. Effects of changes in external K+ and Cl- concentrations suggested that outward currents were carried by K+ and inward by Cl-. Effects of Ca2+ removal from the medium differed between experiments with 0 and 5 mM ATP in the patch pipettes. When pipettes contained no ATP, responses evoked by repeated applications of 10 microM carbachol (0.5-1 min) at 1.5-4 min intervals decreased only slowly after Ca2+ removal, outward currents being reduced to 90 +/- 6% and inward currents to 47 +/- 11% (n = 6) in 10 min. On the other hand, when 5 mM ATP was included in the electrodes, Ca2+ removal abolished the carbachol responses in about 5 min (n = 4). It was also found that tetraethylammonium (5 mM) strongly reduced both currents, by blocking muscarinic receptors, while Ba2+ (2.4 mM) inhibited only the outward K+ current.
authors.affiliation: Department of Oral Surgery, School of Medicine, Nagoya University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shigetomi
authors.forename: T
authors.initials: T
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Ueda
authors.forename: T
authors.initials: T
authors.lastname: Kaneda
authors.forename: H
authors.initials: H
authors.lastname: Tokuno
authors.forename: A
authors.initials: A
authors.lastname: Takai
authors.forename: T
authors.initials: T
authors.lastname: Tomita
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology*; D002469:Cell Separation; D004594:Electrophysiology; D007425:Intracellular Membranes / Q000378:metabolism; D007477:Ions; D010306:Parotid Gland / Q000166:cytology / Q000502:physiology*; D051381:Rats; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
chemical_list: D007477:Ions; D013757:Tetraethylammonium Compounds; D001464:Barium; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate; D002217:Carbachol; D002118:Calcium