1986
DOI: 10.1007/bf01870806
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Influence of external barium and potassium on potassium efflux in depolarized frog sartorius muscles

Abstract: Efflux of 42K+ was measured in frog sartorius muscles equilibrated in depolarizing solutions with external K+ concentrations [( K+]0) between 75 and 300 mM and NaCl concentrations of 60, 120, or 240 mM. For several combinations of KCl and NaCl, steady-state internal potentials (Vi) were the same for different [K+]0. For the range of Vi examined, K+ efflux occurs principally through the K+ inward rectifier channels. When external K+ is removed Vi remains constant for 2 to 3 hr because of the high membrane condu… Show more

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Cited by 10 publications
(13 citation statements)
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“…A residual inward current with linear voltage-dependence, the "leak", was observed at potentials less than Ϫ60 mV after Ba . 24,[52][53][54] In our preparation, the reversal potential of the Ba 2ϩ -sensitive current is Ϫ87 mV, slightly depolarized from E K (Ϫ96 mV, based on a presumed internal K ϩ concentration of ϳ150 mM). This discrepancy may reflect nonideal ionic selectivity for K ϩ over other ions in the setting of physiological ion concentrations (for instance, some IRK channels exhibit low permeability to Ca 2ϩ in low external K ϩ ), 13 or possibly the admixture of additional ionic currents through other channels.…”
Section: Resultsmentioning
confidence: 99%
See 1 more Smart Citation
“…A residual inward current with linear voltage-dependence, the "leak", was observed at potentials less than Ϫ60 mV after Ba . 24,[52][53][54] In our preparation, the reversal potential of the Ba 2ϩ -sensitive current is Ϫ87 mV, slightly depolarized from E K (Ϫ96 mV, based on a presumed internal K ϩ concentration of ϳ150 mM). This discrepancy may reflect nonideal ionic selectivity for K ϩ over other ions in the setting of physiological ion concentrations (for instance, some IRK channels exhibit low permeability to Ca 2ϩ in low external K ϩ ), 13 or possibly the admixture of additional ionic currents through other channels.…”
Section: Resultsmentioning
confidence: 99%
“…16,47 The toxic effect of Ba 2ϩ is thought to be due to its high-affinity block of IRK channels. [52][53][54] Using excised fibers exposed to different concentrations of Ba 2ϩ , we generated experimental support for the notion that the decoupling of V REST from E K under conditions of depleted extracellular K ϩ is indeed a consequence of reduction of the IRK conductance, and that this threshold can be potentiated by partial block of IRK currents. Computer simulations based on these data demonstrate how V REST responds to challenges with low extracellular K ϩ , and how derangements of this response can predispose to aberrant depolarization.…”
Section: Insights Into Resting Potential Abnormalities In Hypokalemicmentioning
confidence: 98%
“…When muscles are equilibrated in either 75 K+/60 Na + solution or in 150 K+/240 Na + solution the internal potential is -22 mV (Spalding, Swift & Horowicz, 1986). The ratio of C1-concentrations, [C1-], for these two solutions is 2.73 and the ratio of the C1-activities, (Cl-), is 2.59 (see Appendix B).…”
Section: Effects Of External [C1-] On Zn 2+ Inhibition Of Ci-effluxmentioning
confidence: 99%
“…One purpose for using high-KC1 equilibrating solutions is that the internal potential of the fibers equals both the chloride and potassium equilibrium potential (Hodgkin & Horowicz, 1959;Spalding et al, 1986). Using standard 3 M KCl-filled glass microelectrode impalement techniques we measured the internal potential of sartorius muscle fibers in high-KCl solutions.…”
Section: Effects Of External [C1-] On Zn 2+ Inhibition Of Ci-effluxmentioning
confidence: 99%
“…In these experiments, 42K+ efflux from sartorius muscles from the frog Rana pipiens was measured using the procedures described in the preceding paper (Spalding, Swift & Horowicz, 1986). K + effiux was calculated as the fraction of radioactive potassium lost from the muscle, expressed as an apparent effiux rate coefficient, k, and referred to simply as "K + efflux" with the units of rain -1.…”
Section: Methodsmentioning
confidence: 99%