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Mouse pancreatic acinar cells: voltage‐clamp study of acetylcholine‐evoked membrane current.
Author(s) -
McCandless M,
Nishiyama A,
Petersen O H,
Philpott H G
Publication year - 1981
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1981.sp013850
Subject(s) - acetylcholine , voltage clamp , current (fluid) , patch clamp , membrane potential , chemistry , membrane , clamp , biophysics , current clamp , endocrinology , medicine , microbiology and biotechnology , electrophysiology , neuroscience , biology , biochemistry , computer science , physics , clamping , computer vision , thermodynamics
1. A two‐micro‐electrode voltage‐clamp technique was applied to a study of the resting properties of mouse pancreatic acinar cell membranes and the action of acetylcholine (ACh). 2. The resting voltage‐current relation was linear. The specific membrane resistance was calculated to be about 10 k omega cm2. This value was doubled after removal of Cl from the tissue bath superfusion solution. 3. At a holding potential equal to the spontaneous resting potential (about ‐35 mV) micro‐ionophoretic ACh application evoked inward current. Reversal of the polarity of the ACh‐evoked current occurred at about ‐ 15 mV. 4. The voltage dependence of the ACh‐evoked current displayed inward rectification. This inward rectification could not be accounted for by the constant field equation. 5. The dose‐response curves for ACh‐evoked inward current were compared in the same units with dose‐response curves for ACh‐evoked depolarization. Half‐maximal depolarization was consistently obtained at a lower dose of ACh than half‐maximal inward current. 6. During steady‐state exposure of the pancreatic tissue segments to Cl‐free sulphate solution the ACh reversal potential was about + 10 mV and the voltage‐current relationship for the ACh‐controlled channels showed inward rectification. Removal of external Na from the Cl‐free solution virtually abolished ACh‐evoked inward current. 7. The resting pancreatic acinar cell membrane is electrically inexcitable. The relative permeabilities of the major monovalent ions appears to be PC1/PNa/PK = 2/0.23/1. The ACh‐evoked inward current is largely carried by Na. Dose‐response curves for ACh‐evoked depolarization and inward current in the same acinar units are different, in such a way that the depolarization response saturates at lower ACh concentrations than the current response.