A K+-selective, three-state channel from fragmented sarcoplasmic reticulum of frog leg muscle

Labarca, Pedro; Miller, Christopher

doi:10.1007/bf01870750

Cited by 98 publications

(69 citation statements)

References 18 publications

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“…Moreover, channels show a voltage-dependent block by decamethonium at a concentration of 0.5-1 mM. These characteristic features of the K ÷ channel in a close to natural lipid environment can be compared with previous results in bilayers [9]. As indicated above, another important application of the new approach reported here is the characterization of single channels in plasma membranes of cells not accessible to conventional patch-clamp measurements.…”

Section: Resultssupporting

confidence: 67%

A membrane fusion strategy for single‐channel recordings of membranes usually non‐accessible to patch‐clamp pipette electrodes

1987

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Membranes of cellular organelles and plasma membranes of some type of cells are not accessible to the high-resolution recordings that the conventional patch-clamp technique allows. However, when these purified membranes are dehydrated together with small lipid vesicles and hydrated again, cell-size vesicles (5-100 llm diameter) are obtained, on which single-channel recordings are possible. This approach, which has been proven successful with about ten different membrane preparations of varied origin, is further illustrated with two examples. First, a known conductivity of the sarcoplasmic reticulum membrane is compared with data obtained by using other techniques. Second, a new sodium current, present at purified postsynaptic membranes from the Torpedo electric organ, is described.

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Section: Resultssupporting

confidence: 67%

A membrane fusion strategy for single‐channel recordings of membranes usually non‐accessible to patch‐clamp pipette electrodes

1987

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“…to cause calcium release, perhaps by blocking the potassium-selective channels in the s.r. membrane (Labarca & Miller, 1981).…”

Section: Potassium Ionsmentioning

confidence: 99%

Extracellular ions and excitation‐contraction coupling in frog twitch muscle fibres.

Miledi¹,

Parker²,

Zhu³

1984

The Journal of Physiology

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SUMMARY1. Intracellular calcium transients were recorded from voltage-clamped frog twitch muscle fibres using Arsenazo III. The possible role of extracellular ions in excitationcontraction (e.-c.) coupling was examined using ion substitutions and blocking drugs in the bathing medium. Parameters measured included the Arsenazo response size to a standard depolarizing pulse (5 ms, 0 mV) and the strength-duration curve for threshold Arsenazo signal.2. Addition of tetrodotoxin (TTX) decreased the response size to small (-30 mV, 5 ms), but not large (+ 30 mV, 10 ms) depolarizations, probably because of poor voltage clamp ofthe tubular membrane in the absence ofTTX. Clamping TTX-treated fibres with the wave form of a recorded action potential gave an Arsenazo response similar to that elicited by the normal action potential (at 10 'C).3. Complete substitution of sodium (by choline, lithium or Tris) or chloride (by methyl sulphate or maleate) in the bathing solution gave no appreciable changes in the size of the Arsenazo response.4. Reduction of extracellular free [Ca2+] to low levels using EGTA caused a slight reduction in the calcium signal elicited by the standard depolarization (to 74 % after a few hours, and to 62 % after 2 days; temperature 5-10 0C). The strength-duration curve was unchanged.5. Arsenazo responses about 75 % of the control size could be elicited in high potassium solution (42 mM-K2SO4) by strong (+ 80 mV, 20 ms) depolarizations, after re-polarizing the fibres to -90 mV for a few minutes. The voltage dependence of activation was shifted to more positive potentials in this solution.6. Tetraethylammonium (TEA) bromide at a concentration of 20 mm did not alter the Arsenazo signal, whilst 120 mM-TEA reduced the response by 25 %. 3,4-diaminopyridine (DAP) reduced the size of the Arsenazo signal at a concentration of 5 mm, and caused spontaneous release of calcium from the sarcoplasmic reticulum (s.r.) in the absence of membrane potential changes. The Arsenazo signal elicited by an action potential was enhanced by 1 mM-DAP, because of prolongation ofthe action potential, but was depressed by higher concentrations.7. We conclude that e.-c. coupling does not involve the influx of any external ions into the muscle fibre. If a current flow between the T-tubules and the s.r. is involved in e.-c. coupling, then this is probably carried by an efflux of potassium ions.

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“…The larger state is reported to have a conductance of 100-150pS in K+ solutions near 100 mm (e.g. Labarca & Miller, 1981;Ide et al 1991;Hirashima, Ishibashi & Kirino, 1991). A substate having a conductance of 60-80 % of the parent state has been reported in SR K+ channels from frog and crustacean skeletal, as well as rabbit and canine cardiac and skeletal, muscle (Larbarca & Miller, 1981;Tomlins, Williams & Montgomery, 1984;Gray, Montgomery & Williams, 1985;Fox, 1985Fox, , 1987Hill, Coronado & Strauss, 1989;Tang et al 1989).…”

Section: Discussionmentioning

confidence: 98%

“…Labarca & Miller (1981) have published estimates of frog SR K+ conductance somewhat lower than this (60 mS cm-2) based on their finding of a zero voltage PO = 0-25. The existence of SR K+ conductances of high magnitude are supported by the recent observation that valinomycin does not lower H+ movement across the SR during Ca2" release suggesting that the normal SR K+ conductance in intact muscle is relatively large and sufficient to provide charge neutralization (Pape, Konishi & Baylor, 1992).…”

Section: Limitations Of the Preparationmentioning

confidence: 95%

Characterization of the potassium channel from frog skeletal muscle sarcoplasmic reticulum membrane.

Wang

Best

1994

The Journal of Physiology

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1. The sarcoplasmic reticulum (SR) membrane of skeletal muscle contains potassium channels which are thought to support charge neutralization during calcium release by providing a permeability pathway for counter-ion movement. To describe the behaviour of the SR K+ channel under physiological conditions, single channel activity was recorded from excised patches of SR membrane. Patches were made from membrane blebs extruded from contracted muscle fibres whose surface membranes had been removed previously by mechanical dissection. 2. The channel was active over a large voltage range from -80 to +100 mV. Ca2`release channel, the SR membrane is known to retard continued Ca2+ efflux (Miller, 1978;Oetliker, 1982).contain ion channels selective for monovalent cations and Thus, the existence of permeability pathways for counteranions (Meissner, 1983;Miller, Bell & Garcia, 1984; Hals, ion movement is thought to be essential for maintaining Stein & Palade, 1989). These channels are thought to allow the large Ca2" flux that occurs during muscle activation.

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A K+-selective, three-state channel from fragmented sarcoplasmic reticulum of frog leg muscle

Cited by 98 publications

References 18 publications

A membrane fusion strategy for single‐channel recordings of membranes usually non‐accessible to patch‐clamp pipette electrodes

A membrane fusion strategy for single‐channel recordings of membranes usually non‐accessible to patch‐clamp pipette electrodes

Extracellular ions and excitation‐contraction coupling in frog twitch muscle fibres.

Characterization of the potassium channel from frog skeletal muscle sarcoplasmic reticulum membrane.

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