Mouse pancreatic acinar cells: voltage-clamp study of acetylcholine-evoked membrane current.
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.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D010179:Pancreas / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology
D002712:Chlorides; D012964:Sodium; D000109:Acetylcholine