Effects of Potassium, Sodium, and Azide on the Ionic Movements That Accompany Activity in Frog Nerves

Asano, Tomoaki; Hurlbut, W P

doi:10.1085/jgp.41.6.1187

Cited by 19 publications

(9 citation statements)

References 16 publications

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“…When this was done, it was assumed that no K 42 was present in the extracellular space. The estimates of intracellular K 42 obtained using equations (1) and (2) agreed with the estimates obtained from washed nerves.…”

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confidence: 73%

Potassium Fluxes in Desheathed Frog Sciatic Nerve

Hurlbut

1963

The Journal of General Physiology

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Desheathed frog (R. pipiens) sciatic nerves were soaked in Nadeficient solutions, and measurements were made of their Na and K contents and of the movements of K 4z. When a nerve is in Ringer's solution, the Na fluxes are equal to the K fluxes, and about 75 per cent of the K influx is due to active transport. The Na content and the Na efflux are linearly related to the Na concentration of the bathing solution, while the K content and the K fluxes are not so related. When a nerve is in a solution in which 75 per cent of the NaG1 has been replaced by choline chloride or sucrose, the active K influx exceeds the active Na effiux, and the K content is maintained. When a nerve is soaked in a solution that contains Li, the K 42 uptake is inhibited, and the nerve loses K and gains Li. When a Li-loaded nerve recovers in a Li-free solution, K is taken up in exchange for Li. This uptake of K requires Na in the external solution. It is concluded that the active transports of K and of Na may be due to different processes, that an accumulation of K occurs only in exchange for an intracellular cation, which need not be Na, and that Na plays a specific, but unknown, role in K transport. I N T R O D U C T I O NT h e effiux of N a f r o m frog sciatic nerves is nearly i n d e p e n d e n t of the K concentration of the bathing solution (7). This suggests that in a nerve in s t a n d a r d Ringer's solution no coupling exists between the active N a efflux and the active K influx. T o prove the independence of the active transport processes for N a a n d K, one must demonstrate also that the active K influx is not directly d e p e n d e n t on the active N a efflux. This report presents results indicating that the active K influx is not stoichiometrically related to the active N a efflux. It is concluded that the active transports of N a and K m a y be b r o u g h t a b o u t b y i n d e p e n d e n t mechanisms. M E T H O D A N D M A T E R I A L SThe method of preparing the nerves and the analytical techniques used in this investigation were the same as those reported in a previous paper (7). The choline content of a nerve was determined with choline labeled with C 14 in the methyl position. x223The Journal of General Physiologyon May 11, 2018 jgp.rupress.org Downloaded from http://doi.org/10.1085/jgp.46.6.1223 Published Online: 1 July, 1963 | Supp Info:Preparation of I~otope Solution 2 mc of K 42 in HC1 were diluted to 5.0 ml with water and adjusted to pH 6-8 with NaOH. Appropriate aliquots of this stock solution were added to the physiological fluids to give convenient levels of radioactivity. The stock solution contained K at concentrations of 30 to 60 raM, and this source of K was allowed for when making up the experimental solutions. Except in some solutions used for loading prior to effiux measurements, the concentrations of K in the experimental radioactive solutions fell within -4-0.1 mw of the standard concentration of 2.0 mM.Uptake o] K 42 Usually, each nerve was soaked in 5 to 10 ml of a solution that contained...

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supporting

confidence: 73%

Potassium Fluxes in Desheathed Frog Sciatic Nerve

Hurlbut

1963

The Journal of General Physiology

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“…Repetitive stimulation of peripheral nerve increases the amount of Nai. The magnitude of the increases in Na+ is inversely proportional to the concentration of K+ present during the bout of stimulation (19 Although we have no definitive evidence, we favor the hypothesis that most of the slow component of the PTP of m and Fmepp results from enhanced Ca2+ entry into the nerve terminal through Ca4+-Nat exchange. Ca2+-Nat exchange has been suggested to account for Cao+ influx into squid axon bathed in normal or low-Na.…”

Section: Discussionmentioning

confidence: 44%

“…These changes in the concentration of Na' had little effect upon the PTP of m or Fmepp. They also have little effect on the quantity of Na+ that accumulates inside frog nerves during repetitive stimulation (19).…”

mentioning

confidence: 99%

Post-tetanic potentiation of acetylcholine release at the frog neuromuscular junction develops after stimulation in Ca2+-free solutions.

Misler¹,

Hurlbut²

1983

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

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At many synapses, previous activity increases the amount of transmitter released by a single action potential. This potentiation oftransmitter release is usually attributed to the local accumulation of the calcium ions that cross the axolemma during an action potential. We found that potentiated transmitter release can be observed at frog neuromuscular junctions after periods of repetitive stimulation in Ca2+-free solutions, if Ca2+ is restored after the tetanus. Potentiation is greater and more prolonged, the lower the level ofextracellular KV. This component ofpotentiation may be due to Ca2+ that accumulates within the terminal in exchange for intracellular Na+.The passage of an action potential along the motor nerve ter-

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“…There is some evidence that this action also occurs in resting desheathed nerve from the frog. Thus, the intracellular content of Na+ is decreased about 20% if the nerves are equilibrated in a modified Ringer's solution containing 8.5 mM K+ (16 take in frog sciatic nerves has not been evident in most of the earlier experiments. However, maintenance of the very high rates of oxygen uptake in nerves treated with dinitrophenol required addition of glucose to the medium (C. M.…”

Section: Methodsmentioning

confidence: 88%

Components of O2-uptake by excised frog nerve dependent upon externally supplied sodium ions.

Brink¹

1975

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

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The steady rate of oxygen uptake of excised frog nerves equilibrated in a solution having a very low concentration of sodium ions increases to a new high steady rate when equilibrated with a solution containing a high concentration of this ion. The increase is suppressed by ouabain, indicating participation of the sodium pump. Part of this sodium-activated increase in oxygen uptake is inhibited by tetrodotoxin, indicating that passive influx of sodium ions into axons is part of the total process. Thus, two pathways for passive sodium influx into axons are suggested by these experiments. Procedures known to increase the passive permeability of axons for sodium ions also increase this sodium-activated oxygen uptake. A mechanism is proposed to explain that part of the sodium-activated oxygen uptake that is inhibited by tetrodotoxin.The regulation of the concentration of sodium ion (Na+) in the cytoplasm of nerve cells is of physiological interest because a low concentration is essential for the maintenance, in the resting state, of the capability for initiation and conduction of the action potential. The generally accepted model of this regulatory system has three interlocking component processes: net passive diffusion of external Na+ into the cytoplasm; activated extrusion of Na+ via a specific ATPase (EC 3.6.1.3; ATP phosphohydrolase) located in the plasma membrane; and rephosphorylation of the product adenosine diphosphate (ADP) by oxidative metabolism in mitochondria (1-4). The first process, dissipating the ionic gradient across the plasma membrane, is offset by the subsequent chemical reactions, and the Na+ gradient is maintained by utilizing oxygen and substrate to provide the necessary supply of adenosine triphosphate (ATP). This model suggests experiments on excised nerves to define further the relations among these processes when all components are interacting as an integrated regulatory system.Ouabain, a potent inhibitor of the membrane-bound adenosine triphosphatase that requires Na+ and K+ for full activity (5), (Na + K)ATPase, has been used to identify that part of Na+-efflux from axons that is transported by the sodium pump (6, 7). Secondarily, the oxygen uptake of excised peripheral nerves has been operationally divided into a ouabain-sensitive and a ouabain-insensitive component (3,(8)(9)(10). The former component is considered to be a measure of that part of the oxidative metabolism that is utilized for extrusion of Na+ from the cytoplasm. For example, the excised sciatic nerve of a frog, Rana pipiens, at rest (i.e., not conducting action potentials) in Ringer's solution uses about [5][6] ,gmol of oxygen per hr/g (dry weight) (11,12). Ouabain reduces this steady-state rate of oxygen uptake about 30% (9). In accordance with the model, these data have been interpreted to mean that 30% of the oxygen uptake of resting nerve is used to extrude Na+ at a rate equal to its influx (3, 9). This process maintains a constant low concentration of this ion in the cytoplasm, as measured in such excised n...

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Effects of Potassium, Sodium, and Azide on the Ionic Movements That Accompany Activity in Frog Nerves

Cited by 19 publications

References 16 publications

Potassium Fluxes in Desheathed Frog Sciatic Nerve

Potassium Fluxes in Desheathed Frog Sciatic Nerve

Post-tetanic potentiation of acetylcholine release at the frog neuromuscular junction develops after stimulation in Ca2+-free solutions.

Components of O2-uptake by excised frog nerve dependent upon externally supplied sodium ions.

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