title: Effect of acetylcholine on electrical properties of subconfluent Madin Darby canine kidney cells.
abstract: To elucidate the effects of acetylcholine on the electrical properties of incompletely confluent Madin Darby canine kidney (MDCK) cells continuous measurements of the potential difference across the cell membrane (PD) were made with conventional microelectrodes during rapid changes of extracellular fluid composition. During control conditions PD averages -48.9 +/- 1.0 mV (n = 51). 1 mumol/l acetylcholine leads to a sustained but reversible hyperpolarization of the cell membrane by -17.9 +/- 0.7 mV (n = 51). Half-maximal effect is observed at some 100 nmol/l. 1 mumol/l atropine does not significantly alter the potential difference across the cell membrane, but abolishes reversibly the hyperpolarizing effect of acetylcholine. Increase of extracellular potassium concentration from 5.4 mmol/l to 20 mmol/l depolarizes the cell membrane by +12.1 +/- 1.1 mV (n = 12) in the absence and by +25.7 +/- 0.9 mV (n = 12) in the presence of acetylcholine. Within 80 s removal of extracellular calcium leads to a depolarization of the cell membrane by +16.2 +/- 3.2 mV (n = 9). In the nominal absence of extracellular calcium acetylcholine leads to a transient hyperpolarization by -13.8 +/- 1.8 mV (n = 9), which can be elicited only once. In conclusion, acetylcholine hyperpolarizes the plasma membrane of MDCK cells by calcium-dependent enhancement of potassium conductance.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D004285:Dogs; D004492:Edetic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D007668:Kidney / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D011188:Potassium / Q000494:pharmacology
chemical_list: D001285:Atropine; D004492:Edetic Acid; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium