Patch-clamp study of rubidium and potassium conductances in single cation channels from mammalian exocrine acini.
Single-channel current recordings were carried out on excised inside-out patches of baso-lateral plasma membrane from exocrine acinar cells. The mouse pancreas and submandibular gland as well as the pig pancreas were investigated. In the mouse pancreas the voltage-insensitive Ca2+-activated cation channel was studied. Single-channel current-voltage (i/v) relationships were studied in symmetrical Rb+-rich solutions and in asymmetrical Rb+/Na+ and Na+/Rb+ solutions. In all cases the i/v relations were linear and had the same slope representing a single-channel conductance of about 33 pS which is identical to that previously obtained with symmetrical Na+ solutions or asymmetrical Na+/K+ solutions. In the mouse submandibular gland and the pig pancreas the voltage and Ca2+-activated K+ channel was studied. The outward currents observed after depolarization in the presence of quasi-physiological Na+/K+ gradients were immediately abolished when all the K+ in the bath fluid was replaced by Rb+ (bath fluid in contact with inside of plasma membrane). This effect was immediately and fully reversible upon return to the high K+ solution. The voltage and Ca2+-activated K+ channel was also studied in asymmetrical K+/Rb+ and Rb+/K+ solutions. In the first case inward (K+) currents could be observed but not outward (Rb+) currents, while in the other case inward (Rb+) currents could not be seen whereas outward (K+) currents were measured. The current-voltage relationships were approximately linear and the null potential was close to 0 mV in both situations.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002412:Cations / Q000378:metabolism*; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology*; D051379:Mice; D010179:Pancreas / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D012413:Rubidium / Q000502:physiology*; D013363:Submandibular Gland / Q000502:physiology*; D013552:Swine
D002412:Cations; D007473:Ion Channels; D012413:Rubidium; D011188:Potassium; D002118:Calcium