The rates of action of K+ and ouabain on the sodium pump in squid axons

Baker, P. F.; Manil, Jacqueline

doi:10.1016/0005-2736(68)90181-8

Cited by 59 publications

(35 citation statements)

References 3 publications

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“…Axons were loaded with 22Na by microinjection and the rate of action of glycoside was determined using the special apparatus described by Baker & Manil (1968) for effecting high speed changes in external solutions. An axon, carefully cleaned of small nerve fibres, is mounted in the outlet arm of a 3-way tap.…”

Section: Measurementm Of Na Effluxmentioning

confidence: 99%

“…The mechanisms by which glycosides inhibit the sodium pump is poorly understood. In many mammalian tissues glycoside-induced inhibition is antagonized by external potassium ions (Glynn, 1964;Baker & Willis, 1970, 1972, but this is less pronounced in the squid axon where inhibition is much more sensitive to external Na ions than to K ions (Baker & Manil, 1968;Baker, 1968).…”

Section: Introductionmentioning

confidence: 99%

“…The present experiments were designed to extend the results of Baker & Manil (1968) on the rates of glycoside-induced inhibition of the sodium pump and to compare these results with the binding of [3H]ouabain. The main conclusions are that in squid axons the binding of ouabain is dependent both on the ionic composition of the external medium and also on the metabolic state of the cell.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Measurementm Of Na Effluxmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…The rapid onset of the neurotransmitter releasing action of ouabain in 'K-free' solution confirms the well-known Na-K competition at the external activation site of the Na-pump (cf. Baker & Willis, 1970; and the Na-dependent binding of ouabain (Baker & Connelly, 1966;Baker, 1968;Baker & Manil, 1968;Baker & Crawford, 1975;Schwartz et al, 1975). Excess Ca (7.5 mM) inhibited the 'K-free' stimulated NA release from pulmonary arteries (Figure lb [3H]-noradrenaline releasing action ofouabain in excess potassium-and/or excess calcium-containing solutions…”

Section: Measurement Of [3h]-noradrenaline Releasementioning

confidence: 99%

“…1968; Baker & Manil, 1968;Baker & Willis, 1970;Baker & Crawford, 1975;Akera, 1977), and can be antagonized by external K . The inhibitory action of external K is the result of the well known Na-K competition at the external activation site ofthe Na-pump (Glynn, 1964; Matsui & Schwartz, 1968;Baker & Willis, 1970;Lindenmayer & Schwartz, 1973;Schwartz et al, 1975;Schwartz, 1976).…”

Section: Introductionmentioning

confidence: 99%

The action of excess potassium and calcium on ouabain‐evoked [³H]‐noradrenaline release from the rabbit pulmonary artery

Magyar¹,

Nguyen²,

Török³

et al. 1986

British J Pharmacology

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[3H]‐noradrenaline ([3H]‐NA) release from the main pulmonary artery of the rabbit has been measured in the presence of neuronal (cocaine, 3 × 10−5 M) and extraneuronal (corticosterone, 5 × 10−5 M) uptake blockers. Removal of K from the external medium increased the [3H]‐NA release. In the absence of external K, ouabain (10−4 M) further enhanced the neurotransmitter release. The ‘K‐free’ stimulated [3H]‐NA release was inhibited by an increase of external Ca (7.5 mM), an action antagonized by ouabain. After preperfusion of the preparations for 30 min with either excess K (23.6 mM) or excess Ca (7.5 mM), the ouabain‐stimulated [3H]‐NA release was inhibited by about 50%; the rates of inhibition did not differ significantly from each other. However, the characteristic initial delay before ouabain‐evoked neurotransmitter release was shortened in excess K, and prolonged in excess Ca‐containing solution. When both excess K and Ca were applied together 30 min before ouabain perfusion, the action of ouabain in releasing neurotransmitter was also inhibited but the rate of inhibition did not differ significantly from that seen when K or Ca were applied separately. The action of K in shortening the initial delay was partly antagonized by Ca. Excess Ca antagonized the inhibition of ouabain‐stimulated [3H]‐NA release caused by excess K when Ca and ouabain were applied together after 30 min preperfusion with excess K‐containing solution. Again excess Ca failed to inhibit the ouabain‐evoked neurotransmitter release if ouabain and excess K were applied together after excess Ca preperfusion (30 min). In both cases the initial delay of ouabain action was greatly shortened. The results suggest a Na‐Ca competition at the external activation site of the nerve terminal sodium‐pump similar to that of Na‐K competition. Furthermore it seems that there is a sort of K‐Ca competition as well, suggested by the finding that excess Ca prevented the inhibition caused by excess K of ouabain‐evoked noradrenaline release and vice versa.

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Purification and molecular properties of the (sodium + potassium)‐adenosinetriphosphatase and reconstitution of coupled sodium and potassium transport in phospholipid vesicles containing purified enzyme

Hokin

1975

J. Exp. Zool.

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Recent work in our laboratory on the purification and characterization of the (sodium + potassium)-activated adenosinetriphosphatase (NaK ATPase) has been reviewed. Two enzymes have been purified, that from the rectal salt gland of the spiny dogfish, Squalus acanthias and that from the electric organ of the electric eel, Electrophorus electricus. The enzyme appears to consist of two catalytic subunits of molecular weight of about 95,000 and one glycoprotein with a molecular weight of about 50,000. The amino acid composition, N-terminal amino acids, and the carbohydrate composition of these subunits have been determined. The phospholipid composition of the holoenzyme has also been determined. The protein component shows very little variation with evolution, but the carbohydrate and phospholipid components show considerable variation. It has been possible to form vesicles from the purified enzyme from Squalus acanthias and to demonstrate the ATP-dependent, ouabain inhibitable, coupled uphill transports of Na+ and K+. The properties of these transports are very similar to those observed previously in intact erythrocytes or resealed erythrocyte ghosts with respect to asymmetries of binding sites, stoichiometries of Na+ and K+ transported, Na+-Na+ exchange, and K+-K+ exchange. It is concluded that the NaK ATPase is the molecular machine for effecting Na+ and K+ transport in the intact cell membrane.

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The rates of action of K+ and ouabain on the sodium pump in squid axons

Cited by 59 publications

References 3 publications

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

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

The action of excess potassium and calcium on ouabain‐evoked [³H]‐noradrenaline release from the rabbit pulmonary artery

Purification and molecular properties of the (sodium + potassium)‐adenosinetriphosphatase and reconstitution of coupled sodium and potassium transport in phospholipid vesicles containing purified enzyme

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The rates of action of K+ and ouabain on the sodium pump in squid axons

Cited by 59 publications

References 3 publications

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

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

The action of excess potassium and calcium on ouabain‐evoked [3H]‐noradrenaline release from the rabbit pulmonary artery

Purification and molecular properties of the (sodium + potassium)‐adenosinetriphosphatase and reconstitution of coupled sodium and potassium transport in phospholipid vesicles containing purified enzyme

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The action of excess potassium and calcium on ouabain‐evoked [³H]‐noradrenaline release from the rabbit pulmonary artery