Ion Permeation in Cell Membranes

Pappone, Pamela A.; Cahalan, Michael D.

doi:10.1007/978-1-4613-1943-6_15

Cited by 2 publications

(1 citation statement)

References 281 publications

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“…Na + and Cs + were almost impermeant, with an upper limit for their permeability ratios of 0.03 and 0.02, respectively. This selectivity sequence of K + > Rb + > NH~ > Na + = Cs + is similar to that found in delayed rectifier and many other K channels (Hille, 1984;Pappone and Cahalan, 1986). c, ati.g…”

Section: Selectivitysupporting

confidence: 81%

Voltage-gated potassium channels in brown fat cells.

Lucero

Pappone

1989

The Journal of General Physiology

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We studied the membrane currents of isolated cultured brown fat cells from neonatal rats using whole-cell and single-channel voltage-clamp recording. All brown fat cells that were recorded from had voltage-gated K currents as their predominant membrane current. No inward currents were seen in these experiments. The K currents of brown fat cells resemble the delayed rectifier currents of nerve and muscle cells. The channels were highly selective for K § showing a 58-mV change in reversal potential for a 10-fold change in the external [K+]. Their selectivity was typical for K channels, with relative permeabilities of K § > Rb § > NH~ >> Cs +, Na +. The K currents in brown adipocytes activated with a sigmoidal delay after depolarizations to membrane potentials positive to -50 mV. Activation was half maximal at a potential of -28 mV and did not require the presence of significant concentrations of internal calcium. Maximal voltage-activated K conductance averaged 20 nS in high external K § solutions. The K currents inactivated slowly with sustained depolarization with time constants for the inactivation process on the order of hundreds of milliseconds to tens of seconds. The K channels had an average sin#e-channel conductance of 9 pS and a channel density of ~ 1,000 channels/cell. The K current was blocked by tetraethylammonium or 4-aminopyridine with half maximal block occurring at concentrations of 1-2 mM for either blocker. K currents were unaffected by two blockers of Ca2+-activated K channels, charybdotoxin and apamin. Bath-applied norepinephrine did not affect the K currents or other membrane currents under our experimental conditions. These properties of the K channels indicate that they could produce an increase in the K § permeability of the brown fat cell membrane during the depolarization that accompanies norepinephrine-stimulated thermogenesis, but that they do not contribute directly to the norepinephrine-induced depolarization.

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Section: Selectivitysupporting

confidence: 81%