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Alkali cation permeability and caesium blockade of cromakalim-activated current in guinea-pig ventricular myocytes.

Abstract : 1. The sensitivity of cromakalim-activated current (Icrom) to manipulations of extracellular cationic composition was examined in whole-cell voltage clamp recordings from freshly-dispersed, adult guinea-pig ventricular myocytes. In bathing media with different concentrations of K+ (1, 2.5, 5.4 and 12 mM) the Icrom reversal potential (Erev) varied in strict correspondance with the K+ equilibrium potential and inward Icrom amplitude was proportional to the external K+ concentration. 2. Replacement of 12mM K+ with 12mM Rb+ induced a slight positive shift of Erev indicating that PRb+/PK+ = 1.06. K+ replacement with 12mM Cs+ reduced or abolished inward Icrom and produced a negative shift of Erev by at least 50 mV; an upper limit of PCs+/PK+ was fixed at 0.18. 3. Addition of Rb+ (1-30 mM) to 2.5 mM K(+)-containing medium produced a concentration-dependent increase in inward Icrom and positive shift of Erev suggesting that K+ and Rb+ have similar permeabilities and conductivities and do not interfere with each other in the channel. 4. CS+ (0.01-30 mM), added to medium containing 12 mM Rb+, induced a potent, voltage-dependent inhibition of inwardly rectifying current (IK1; IC50 = 0.2-3 mM). Voltage-dependent inhibition of inward Icrom was observed only at considerably higher CS+ concentrations (IC50 = 4-30 mM). Extracellular Rb+ and CS+ did not substantially alter the amplitude of outward Icrom. 5. The results support the contention that the ATP-sensitive K+ channel is the primary target of cromakalim action in ventricular myocytes.
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Contributor : Stéphane Oliet Connect in order to contact the contributor
Submitted on : Friday, March 31, 2006 - 10:38:35 AM
Last modification on : Tuesday, November 5, 2019 - 10:00:07 AM


  • HAL Id : inserm-00000090, version 1
  • PUBMED : 1718524



John Randle, Stéphane H. R. Oliet, Jean-François Renaud. Alkali cation permeability and caesium blockade of cromakalim-activated current in guinea-pig ventricular myocytes.. British Journal of Pharmacology, Wiley, 1991, 103, pp.1795-801. ⟨inserm-00000090⟩



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