Activation of Ca2+-dependent Cl- and K+ conductances in rat and mouse parotid acinar cells.
Isolated acinar cells from rat and mouse parotid glands were studied with patch-clamp whole-cell current recordings. Acetylcholine (ACh) stimulation caused a transient inward current at a membrane potential of -70 mV, and a sustained outward current at a membrane potential of 0 mV, in quasi physiological Na+, K+ ion gradients, except the zero-Cl- ion gradient condition across the membrane. The reversal potential obtained from the ACh-evoked steady current was about -75 mV, in this ionic condition. When major Cl- ions of both the pipette and the bath solution were replaced, either by glutamate or by sulphate, only a large outward current was observed, at a membrane potential of -60 mV, in the presence of ACh. The addition of Ca2+-ionophore A23187 caused responses similar to those evoked by ACh. The reversal potential of A23187-induced current was close to the K+ equilibrium potential of -90 mV, in a Cl- -free condition. When K+-free NaCl solution was used in the pipette and the bath, A23187 caused only a large inward current, at a membrane potential of -60 mV. The reversal potential of A23187-evoked current was about -15 mV, in a symmetrical K+-free, NaCl condition. These results suggest that the ACh and A23187 activate Cl- as well as K+ conducting pathways via an increase in [Ca2+]i in the parotid acinar cells. The A23187-evoked large K+ current could not be explained solely by a rise in open probability of the channels.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D010306:Parotid Gland / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D051381:Rats
D002712:Chlorides; D000001:Calcimycin; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium