Pancreatic acinar cells: ionic dependence of the membrane potential and acetycholine-induced depolarization.
1. Intracellular recordings of membrane potentials have been made in vitro from the exocrine acinar cells of the mouse pancreas using glass micro-electrodes.2. The mean membrane potential of the acinar cells during superfusion with Krebs-Henseleit solution was -39.2 mV. Increasing [K](o) tenfold decreased the membrane potential by 28 mV when [K](o) was above 10 mM. This depolarization was not affected by atropine (1.4 x 10(-6)M). Strophanthin-G (10(-3)M) slowly depolarized the cells at about 10 mV hr(-1).3. Brief exposure to acetylcholine (ACh), 5.5 x 10(-5)M, or pancreozymin resulted in a short lasting depolarization of the acinar cells. Atropine (1.4 x 10(-6)M) blocked the depolarizing action of ACh but not that of pancreozymin. Adrenaline (5.5 x 10(-5)M) or cyclic AMP (10(-3)-10(-4)M) did not influence the membrane potential.4. The amplitude of the ACh-induced depolarization was not dependent on the presence of CO(2)/HCO(3) in the bathing fluid, but it was closely dependent on the extracellular Na concentration. However, ACh was still able to evoke a small depolarization even after prolonged exposure of the tissue to a Na-free solution.5. During exposure of the tissue to a Ca-free solution the resting membrane potential was decreased and the ACh-induced depolarization was significantly reduced. Some substances which are known in other tissues to inhibit membrane Ca(2+) currents, i.e. La(3+), D-600 and tetracaine, were able to reduce, but never abolish, the ACh-induced depolarization.6. These results suggest that the effect of ACh on the pancreatic acinar cell is to increase the permeability of the membrane to commonly occurring ions with a consequent Na-influx and a small Ca-influx.
D000109:Acetylcholine / Q000494:pharmacology*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002766:Cholecystokinin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D010179:Pancreas / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013328:Strophanthins / Q000494:pharmacology; D013748:Tetracaine / Q000494:pharmacology
D004140:Dinitrophenols; D013328:Strophanthins; D013748:Tetracaine; D001285:Atropine; D000584:Amiloride; D002766:Cholecystokinin; D012964:Sodium; D000242:Cyclic AMP; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium; D004837:Epinephrine