Effects of intracellular adenosine-5'-diphosphate and orthophosphate on the sensitivity of sodium efflux from squid axon to external sodium and potassium.
TLDR
An outline is presented for a model which might explain the effects of ADP, Pi and deoxy-ATP, and it is shown that sodium efflux is maximally Ko-dependent when the ATP:ADP ratio is about 10:1, becomes insensitive to Ko when the ratios are about 1:2, and is inhibited byKo when the ratio isAbout 1:10.Abstract:
A study was made of sodium efflux from squid giant axon, and its sensitivity to external K and Na. When sodium efflux from untreated axons was strongly stimulated by Ko, Nao was inhibitory; when dependence on Ko was low, Nao had a stimulatory effect. Incipient CN poisoning or apyrase injection, which produces high intracellular levels of ADP1 and Pi, rendered sodium efflux less dependent on external K and more dependent on external Na. Injection of ADP, AMP, arginine, or creatine + creatine phosphokinase, all of which raise ADP levels without raising Pi levels, had the same effect as incipient CN poisoning. Pi injection had no effect on the K sensitivity of sodium efflux. Axons depleted of arginine and phosphoarginine by injection of arginase still lost their K sensitivity when the ATP:ADP ratio was lowered and regained it partially when the ratio was raised. Rough calculations show that sodium efflux is maximally Ko-dependent when the ATP:ADP ratio is about 10:1, becomes insensitive to Ko when the ratio is about 1:2, and is inhibited by Ko when the ratio is about 1:10. Deoxy-ATP mimicked ADP when injected into intact axons. Excess Mg, as well as Pi, inhibited both strophanthidin-sensitive and strophanthidin-insensitive sodium efflux. An outline is presented for a model which might explain the effects of ADP, Pi and deoxy-ATP.read more
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Book ChapterDOI
Na,K-ATPase: Reaction Mechanisms and Ion Translocating Steps
TL;DR: This chapter summarizes some selected facts that may have bearing on the question: to what extent, and in how much detail, can the biophysical observations on the operation of the sodium pump be reconciled with what is known about the biochemical reaction mechanism of the Na, K–ATPase.
Journal ArticleDOI
Sodium efflux in Myxicola giant axons.
TL;DR: Several properties of the Na pump in giant axons from the marine annelid Myxicola infundibulum have been determined in an attempt to characterize this preparation for membrane transport studies and the effect of elevated Nai on the Na efflux was determined.
Book ChapterDOI
Different approaches to the mechanism of the sodium pump.
I. M. Glynn,S. J. D. Karlish +1 more
TL;DR: The way in which the sodium pump uses energy from the hydrolysis of ATP to perform osmotic and electrical work is not yet understood and a number of different approaches to this problem are attempted.
Journal ArticleDOI
Energetics of sodium transport in the urinary bladder of the toad. Effect of aldosterone and sodium cyanide.
TL;DR: Results support the view that the stimulatory effects of aldosterone on sodium transport involve an increase in ATP or (ATP)/(ADP) X (Pi), as measured by the short circuit current and the concentration of ATP.
Journal ArticleDOI
Strophanthidin-induced sodium efflux.
L. Beauge,L. J. Mullins +1 more
TL;DR: The present results suggest that the strophanthidin-induced Na efflux represents the outward component of an exchange of ions in which internal Na is exchanged for external monovalent cations.
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