A comparison of the phosphorus metabolism of intact squid nerve with that of the isolated axoplasm and sheath.

Baker, P. F.; Shaw, T. I.

doi:10.1113/jphysiol.1965.sp007710

Cited by 59 publications

(30 citation statements)

References 13 publications

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“…Giant axons were removed from Loligo pealei captured at the Marine Biological Laboratory (Woods Hole, MA). Axoplasm was collected by the roller extrusion method (10). Sections of giant axon (5-7 cm long) were removed, stored, and cleaned in Ca2+-free artificial seawater.…”

Section: Methodsmentioning

confidence: 99%

Ion channels in transit: voltage-gated Na and K channels in axoplasmic organelles of the squid Loligo pealei.

Wonderlin¹,

French²

1991

Proc. Natl. Acad. Sci. U.S.A.

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Ion channels that give rise to the excitable properties of the neuronal plasma membrane are synthesized, transported, and degraded in cytoplasmic organelles. To determine whether plasma membrane ion channels from these organelles could be physiologically activated, we extruded axoplasm from squid giant axons, dissociated organelles from the cytoskeletal matrix, and fused the free organelles with planar lipid bilayers. Three classes of ion channels normally associated with the plasma membrane were identified based on conductance, selectivity, and gating properties determined from steady-state single-channel recordings: (i) voltagedependent Na channels, (it) voltage-dependent delayed rectifier K channels, and (iiW) large, voltage-independent K channels. The identity of the delayed rectifier channels was confirmed by reconstructing the time course of activation from singlechannel responses to depolarizing voltage steps applied across the bilayer. These observations suggest that several classes of plasma membrane ion channels are transported in cytoplasmic organelles in physiologically active forms.

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Section: Methodsmentioning

confidence: 99%

Ion channels in transit: voltage-gated Na and K channels in axoplasmic organelles of the squid Loligo pealei.

Wonderlin¹,

French²

1991

Proc. Natl. Acad. Sci. U.S.A.

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“…Fully poisoned axons differ in a number of respects from unpoisoned or partially poisoned axons. They have much less ATP, but more ADP, AMP and Pi (Caldwell, 1960;Baker & Shaw, 1965) and the intracellular concentration of ionized Ca is increased about thirtyfold (Baker, Hodgkin & Ridgway, 1971). Any or a combination of these factors might be responsible for the reduced rate of glycoside binding.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of the sodium pump in squid axons by cardiac glycosides: dependence on extracellular ions and metabolism

Baker¹,

Willis²

1972

The Journal of Physiology

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SUMMARY1. The rate of inhibition of the Na pump by ouabain was examined both by direct measurement of the rate of decline of the Na efflux and by the binding of [3H]ouabain.2. The onset of inhibition of the Na efflux was concentration-dependent; but did not follow simple first order kinetics. The time course of inhibition was roughly exponential although in about 30 % of the axons inhibition was preceded by a transient stimulation of the Na efflux.3. Inhibition of the Na efflux by both ouabain and strophanthidin was apparently irreversible.4. The onset of inhibition was slowed markedly at low temperatures. 5. Replacement of external Na by choline, dextrose or potassium slowed the rate of inhibition. Li behaved like Na and inhibition was faster in K-ASW than in choline-ASW.6. The rate of inhibition of Na-Na exchange was similar to that of Na-K exchange, but ouabain failed to bind securely to fully poisoned axons.7. Two components of [3H]ouabain-binding could be distinguished. A linear component which probably reflects uptake into the cells and a saturable component which seems to reflect binding to Na-pumping sites.8. The saturable component of binding followed a similar time course to the inhibition of the Na efflux and the rate of binding was reduced in choline-ASW and in fully poisoned axons.9. Measurements of [3H]ouabain-binding indicate that the number ofNa pumping sites in the axon membrane is probably between 103 and 104/,u2.

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“…However, it appears very probable that, fundamentally, the rate of Na extrusion is a saturable function of some power (probably 3) of internal Na concentration (Keynes & Swan, 1959;Rang & Ritchie, 1968;Garay & Garrahan, 1973 The rate constant for Na extrusion from sympathetic ganglion cells is high (a 0 35 min-' at 250 C) implying an appropriately high energy consumption and oxygen requirement. For example, at rest a steady pumped efflux of about 5-8 m-mole (kg cell fluid)-' min-' may be deduced, necessitating an oxygen consumption rate of 0-13 mole 02 (g wet tissue weight)-' min-' at Na: P and P: 0 ratios of 3:1 (Glynn, 1962;Baker & Shaw, 1965;McIlwain, 1966). This is about 42 % of the resting 02 consumption at 240 C (Larrabee, 1958) (111 eumole (g dry weight)-' hr-' = 0-31 mole.…”

Section: Discussionmentioning

confidence: 99%

Movements of labelled sodium ions in isolated rat superior cervical ganglia

Brown¹,

Scholfield²

1974

The Journal of Physiology

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SUMMARY1. Isolated rat superior cervical ganglia were incubated in Krebs solution containing 24Na and carbachol for 4 min at 250 C. They were then washed at 30 C for 15 min to remove extracellular 24Na and the efflux of residual intracellular 24Na stimulated by warming to 250 C.2. During the 15 min wash at 30 C desaturation curves became exponential with a rate constant of 0-012 + 0 001 min-' (n = 24). This was assumed to represent loss of intracellular 2MNa, and initial uptake of 24Na was calculated therefrom by back-extrapolation to zero wash-time. After 4 min in 24Na + 180,u/M carbachol intracellular [24Na] so calculated was 61-6 + 341 mM (n = 18), representing 83 % labelling of intracellular Na.In the absence of carbachol intracellular [24Na] was 10-0 + 0-5 mM, representing 49 % labelling. Extracellular Na was labelled by > 90 % after 4 min in "Na. The apparent rate constant for washout of extracellular 2ANa was 0-6 min-' at 30 C and 0-95 min-' at 250 C.3. The loss of the residual intracellular 2MNa during temperature stimulation was interpreted quantitatively in terms of an exponential decline of the bulk of intracellular 24Na with an extrusion rate constant of 0-39 + 0-1 min-' (n = 18), efflux being delayed by passage through the extracellular space with an effective rate constant of 0-8-1-2 min-. 8. The properties of the ganglionic Na pump deduced from rates of temperature-stimulated 2MNa extrusion accord with the view that the ganglion hyperpolarization observed after Na loading by exposure to nicotinic depolarizing agents results from electrogenic Na extrusion. A comparable hyperpolarization is observed after temperature stimulation following Na loading.

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A comparison of the phosphorus metabolism of intact squid nerve with that of the isolated axoplasm and sheath.

Cited by 59 publications

References 13 publications

Ion channels in transit: voltage-gated Na and K channels in axoplasmic organelles of the squid Loligo pealei.

Ion channels in transit: voltage-gated Na and K channels in axoplasmic organelles of the squid Loligo pealei.

Inhibition of the sodium pump in squid axons by cardiac glycosides: dependence on extracellular ions and metabolism

Movements of labelled sodium ions in isolated rat superior cervical ganglia

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