Basolateral K+ conductances in surface epithelium of Necturus antrum: effects of Ca2+ and divalent cations.
Intracellular microelectrode techniques were used to characterize basolateral membrane K+ conductances in isolated Necturus antral mucosa. Exposure of tissues to progressively higher levels of serosal K+ (4, 20, 40, or 60 mM) resulted in progressively greater depolarizations of basolateral membrane potentials and decreases in membrane resistance, consistent with the presence of a significant K+ conductance. Ba2+ (2 mM) partially blocks these conductances. Exposure of tissues to increased levels of serosal Ca2+ (from 1.8 to 6.8 mM) elicited significant hyperpolarization of basolateral potentials and decreases in basolateral resistance. These effects are also elicited by Sr2+ (5 mM), but not by Mg2+ (5 mM). Ba2+ (5 mM) elicits complex and time-dependent effects, but transiently elicits an effect similar to high Ca2+. Ion substitutions in the serosal perfusate suggest that the Ca(2+)-induced effects are due to enhancement of basolateral K+ conductances. Further work is necessary to identify the processes that mediate this increase in basolateral K+ conductance and to evaluate the physiological significance of this change in membrane permeability to K+.
Soybel
D I
DI
Department of Surgery, Yale University School of Medicine, New Haven, Connecticut 06510.
Ashley
S W
SW
Cheung
L Y
LY
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004848:Epithelium / Q000502:physiology; D009994:Osmolar Concentration; D011188:Potassium / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D011706:Pyloric Antrum / Q000502:physiology*; D012704:Serous Membrane / Q000378:metabolism
D002413:Cations, Divalent; D011188:Potassium; D002118:Calcium