Mouse pancreatic acinar cells: voltage‐clamp study of acetylcholine‐evoked membrane current.

Abstract

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.

Stimulus‐secretion coupling: cytoplasmic calcium signals and the control of ion channels in exocrine acinar cells.

“…Figure 2 shows voltage-clamp records of ACh-evoked transmembrane current and the measurement of EA(-.h under the control condition and during prolonged exposure to a Cl--free sulphate solution. The data from the voltage-clamp current recording experiments (McCandless et al 1981) are in good agreement with the earlier determination of EAch using potential recordings (Iwatsuki & Petersen, 1977b).…”

“…That there is a regulated Na+ conductance pathway in the mouse pancreatic acinar cell membrane (Matthews & Petersen, 1973;Nishiyama & Petersen, 1975;McCandless et al 1981;Petersen et al 1981) is beyond doubt, but I misinterpreted the data in the salivary and lacrimal glands and erroneously concluded that there was also such a Na' conductance in these glands (Petersen, 1980a). This led to my strongly expressed belief that the stimulant-evoked Na+ influx through regulated channels in the basolateral membrane was the most important and general feature in all the exocrine STIMUL LUS-SECRETION COUPLINVG glands (Petersen, 1980a).…”

“…The changes that have occurred since then can be divided into three main phases. First, there was a period dominated by an increasingly sophisticated use of intracellular microelectrodes ending with the first voltage-clamp studies on communicating acinar cell networks (McCandless, Nishiyama, Petersen & Philpott, 1981;Maruyama & Petersen, 1983). During this period the first evidence for a link between receptor-activated intracellular Caa2+ release and the opening of ion channels was obtained (Iwatsuki & Petersen, 1977c) and the various electrogenic transport pathways in the acinar cell membranes were mapped (Petersen, 1980a).…”

“…ACh applications were of 100 nA strength (0-3 s duration) (retaining current 20 nA). A, C and D are adapted from McCandless et al 1981. B is adapted from Maruyama & Petersen, 1983. 7 0.11.…”

Electrogenic properties of the sodium-alanine cotransporter in pancreatic acinar cells: I. Tight-seal whole-cell recordings

“…The effect of Rs on the observed transmembrahe currents was always negligible. The specific membrane resistance RM = Rr~A was calculated from R,~ and Cm assuming a specific membrane ca- Petersen & Philpott, 1981). tn many cases small clusters consisting of 2 to 5 cells were used instead of single cells for measuring alanine-driven currents.…”