The effect of temperature on the electrical activity of the giant axon of the squid

Hodgkin, A. L.; Katz, Bernhard

doi:10.1113/jphysiol.1949.sp004388

Cited by 530 publications

(319 citation statements)

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“…An alternative method for describing ion fluxes coupled to chemical reaction rates uses the law of mass action to describe the dependence of the rates on the concentrations of the reactants and the membrane potential [26,27]. Using this method, qualitatively (though not quantitatively) identical results are obtained.…”

Section: Lizsupporting

confidence: 48%

The Residual Protonmotive Force in Mitochondria after an Oxygen Pulse

Heinz

Westerhoff

Dam

2005

European Journal of Biochemistry

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Both from irreversible thermodynamics and from mass-action kinetics it can be derived that upon anaerobiosis in an oxygen-pulse experiment the protonmotive force across a mitochondrial membrane undergoes a sudden drop. Under representative conditions the protonmotive force after the drop (the residual protonmotive force) is shown to be less than 3 kJ . [7,11] or 3 [12]. Most of the data are based on a particular type of experiment, i.e. the observation of the number of protons ejected from mitochondria that receive a known amount of substrate (either oxygen, succinate or ATP). A different approach is to compare the phosphorylation potential to the protonmotive force in state-4 mitochondria. This leads to estimation of H+/ATP stoichiometries of 2.5 or higher [13-161. This latter method, however, is not useful for the determination of the H+/O ratios as long as the cytochrome c oxidase reaction cannot be reversed experimentally.An essentially new method for the determination of stoichiometric numbers was developed by taking into account mechanistic parameters when formulating flow-force relations in terms of irreversible thermodynamics [17,18]. Using the derived equations the stoichiometric numbers can in principle be determined under all conditions of oxidation and/or phosphorylation. Initially this method had the disadvantage of being based on the assumption that the relations between reaction/diffusion rates (flows) and their driving forces are proportional. A proof of such proportionality only existed for systems much closer to equilibrium than some processes occurring in mitochondrial oxidative phosphorylation [19]. Investigation of the nature of these flow/force relations for enzyme-catalyzed systems obeying certain, reasonable, boundary conditions [20,21] allowed us to modify the equations in the description, so that it could be applied to mitochondrial oxidative phosphorylation [22].Application of this method enables the experimentor to determine the H+/O and H+/-P stoichiometric numbers under the condition of oxidative phosphorylation, rather than under conditions where the protonmotive force has been eliminated [3 -91. The results of such an application [22] (H+/O = 3.6 for succinate, H + / -P = 2.4) are of course, in agreement with only some of the values determined previously. Evidently, unequivocal results have to emerge from oxygen-pulse experiments before they can be compared with the results obtained with our new quantitative method.In order to try to establish the origin of the conflicting results obtained with oxygen-pulse experiments we set out to reexamine how stoichiometric numbers are derived from oxygen-pulse experiments.In this article we show that, at the time that the oxygen has been consumed, the protonmotive force may drop rapidly and considerably. Thus back extrapolation of the proton re-entrance into the mitochondria is not enough to correct for proton leakage during the oxidation-driven proton extrusion. The values calculated on the basis of such extrapolations must be underestimate...

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Section: Lizsupporting

confidence: 48%

The Residual Protonmotive Force in Mitochondria after an Oxygen Pulse

Heinz

Westerhoff

Dam

2005

European Journal of Biochemistry

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“…In additio'i, the enzyme contributes to the establishment of membmne potential [4,5] and is critical for the regulation of cell volume and osmotic pressure. Finally, the Na,K-ATPase is the receptor for cardiac glycosides, mediating the effects of these drugs on cardiac function.…”

Section: Introductionmentioning

confidence: 99%

Critical effects on catalytic function produced by amino acid substitutions at Asp⁸⁰⁴ and Asp⁸⁰⁸ of the al isoform of Na,K‐ATPase

1996

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At two intramembrane carboxyl-containing amino acids of the sheep al isoform of Na,K-ATPase (Aspso and Aspass), both charge-conserving (Asp to Glu) and charge-deleting (Asp to Asn, Leu and Ala) replacements were made and the altered enzymes studied. Nucleotide changes encoding the amino acid substitutions were placed in a cDNA encoding a ouabainresistant enzyme (sheep al RD) and the encoded enzymes were expressed in ouabain-sensitive HeLa cells. Transfections with cDNAs carrying all As so4 L carrying AspsesAla, Asp substitutions, along with those Asn, and AspSOSLeu replacements failed to confer ouabain resistance to the cells, indicating critical roles for Aspse4 and AspSo*. Only the expression of the Aspso8Glu enzyme produced ouabain-resistant HeLa cells, demonstrating that the altered protein was functional. When the inactive proteins Aspsa4Ala and AspsasAla were expressed using an alternative selection system (the protein carrying the amino acid substitution was the ouabain-sensitive wild-type sheep al Na,K-ATPase, which was expressed in ouabain-resistant 3T3 cells), intact cells were able to bind extracellular ouabain with high affinity (& = l-30 nM), indicating that the inactive proteins were synthesized and folded properly in the plasma membrane. The results demonstrate that carboxyl side chains at positions 8oJ and 808 are critical for enzyme catalytic function.

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“…2). At comparable temperatures Hodgkin and Katz (26) There seemed to be no direct correlation between the initial resting poten-6 The value for Ca ++ is calculated on the basis of Hodgkin and K~tz' (27) conclusion that the squid axoplasm probably contains 3 X 10 -4 ~ Ca ++. The axonal concentration of Mg ++ is unknown.…”

Section: Resting and Action Potentials Before Injectionmentioning

confidence: 99%

Bioelectric Effects of Ions Microinjected Into the Giant Axon of Loligo

Grundfest

Kao

Altamirano

1954

Journal of General Physiology

103

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1. A technique is described for recording the bioelectric activity of the squid giant axon during and following alteration of the internal axonal composition with respect to ions or other substances. 2. Experimental evidence indicates that the technique as described is capable of measuring changes in local bioelectric activity with an accuracy of 10 to 15 per cent or higher. 3. Alterations of the internal K+ or Cl- concentrations do not cause the change in resting potential expected on the basis of a Donnan mechanism. 4. The general effect of microinjection of K+ Rb+, Na+, Li+, Ba++, Ca++, Mg++, or Sr++ is to cause decrease in spike amplitude, followed by propagation block. 5. The resting potential decreases when the amplitude of the spike becomes low and block is incipient. 6. The decrease in resting potential and spike amplitude may be confined to the immediate vicinity of the injection. 7. At block, the resting potential decreases up to 50 per cent, but injection of small quantities of divalent cations may cause much larger localized depolarization. 8. The blocking effectiveness of K+, Na+, and Ca++ expressed as reciprocals of the relative amounts needed to cause block is approximately 1:5:100. Rb+ has the same low effectiveness as does K+. Li+ resembles Na+. Ba++ and Mg++ are approximately as effective as Ca++. 9. Microinjection of Na+ may cause marked prolongation of the spike at the injection site as well as decrease in its amplitude. 10. The anions used (Cl-, HCO3-, NO3-, SO4-, aspartate, and glutamate) do not seem to exert specific effects. 11. A tentative explanation is offered for the insensitivity of the resting potential to changes in the axonal ionic composition. 12. New data are presented on the range of variation, in a large sample, of the magnitude of the resting potential and spike amplitude.

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The effect of temperature on the electrical activity of the giant axon of the squid

Cited by 530 publications

References 4 publications

The Residual Protonmotive Force in Mitochondria after an Oxygen Pulse

The Residual Protonmotive Force in Mitochondria after an Oxygen Pulse

Critical effects on catalytic function produced by amino acid substitutions at Asp⁸⁰⁴ and Asp⁸⁰⁸ of the al isoform of Na,K‐ATPase

Bioelectric Effects of Ions Microinjected Into the Giant Axon of Loligo

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The effect of temperature on the electrical activity of the giant axon of the squid

Cited by 530 publications

References 4 publications

The Residual Protonmotive Force in Mitochondria after an Oxygen Pulse

The Residual Protonmotive Force in Mitochondria after an Oxygen Pulse

Critical effects on catalytic function produced by amino acid substitutions at Asp804 and Asp808 of the al isoform of Na,K‐ATPase

Bioelectric Effects of Ions Microinjected Into the Giant Axon of Loligo

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Critical effects on catalytic function produced by amino acid substitutions at Asp⁸⁰⁴ and Asp⁸⁰⁸ of the al isoform of Na,K‐ATPase