Rb+, Cs+ ions and the inwardly rectifying K+ channels in guinea-pig ventricular cells.
Rb+ and Cs+ ion permeability and the effects of these ions from the inside on the inwardly rectifying K+ channel were studied in guinea-pig ventricular cells. A total substitution of either Rb+ or Cs+ for external K+ in the outside-out configuration of the patch-clamp technique abolished the inward current. The outward current carried by K+ was recorded. The unitary amplitude was reduced to about half of the control value with Rb+ but was not changed with Cs+. Internal Rb+ and Cs+, at a concentration of 10-40 mM, reduced the unitary amplitude of the outward current. No substate behaviour was observed. The reversal potential was +18 mV after replacing 105 mM internal K+ with Rb+ at 150 mM external K+. This value gives a permeability ratio of Rb+ to K+ of 0.27. Under a total substitution of Rb+ or Cs+ for internal K+, the outward currents were not measurable. Cs+ induced flickering in the inward current carried by K+. It is thus concluded that Rb+ and Cs+ ions are not measurably permeant at the single-channel level but permit K+ permeation in place of external K+ and that internal Rb+ and Cs+ produce a voltage-dependent block of the channel with fast kinetics.
Matsuda
H
H
Department of Physiology, Kansai Medical University, Moriguchi, Osaka 570, Japan.
D000818:Animals; D002586:Cesium / Q000494:pharmacology / Q000502:physiology*; D004553:Electric Conductivity; D006168:Guinea Pigs; D007477:Ions; D007700:Kinetics; D010539:Permeability; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D012413:Rubidium / Q000494:pharmacology / Q000502:physiology*; D012996:Solutions; D016276:Ventricular Function
D007477:Ions; D015221:Potassium Channels; D012996:Solutions; D002586:Cesium; D012413:Rubidium; D011188:Potassium