The Sodium Pump

Glynn, I. M.; Karlish, Steven J. D.

doi:10.1146/annurev.ph.37.030175.000305

Cited by 866 publications

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“…According to Glynn & Karlish (1975) active transport of K+ across plasmatic membranes can be stimulated by a rise, or depressed by a reduction, of the K+ content in the extracellular fluid. Consequently the amount of K+ which is transported by dark cells can vary according to its perilymphatic level.…”

Section: Discussionmentioning

confidence: 99%

Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog.

Valli

Zucca

Botta

1990

The Journal of Physiology

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SUMMARY1. Endolymphatic and perilymphatic potassium concentrations were measured with K+-sensitive microelectrodes in isolated semicircular canals of the frog. K+ levels were evaluated both at rest and during sinusoidal stimulation (0-05 Hz) of the sensory organ.2. Mechanical stimulation of hair cells was associated with sinusoidal changes (about 0-2 mM) in the perilymphatic K+ concentration.3. Perilymphatic K+-fluctuations were modified neither by impairment of the synaptic transmission at cyto-neural junctions nor by chronic denervation of the crista ampullaris, thus indicating that K+ ions were actually released by hair cells.4. Voltage-clamp experiments of the whole sensory organ showed that K+ flows across the crista ampullaris can vary from 3 x 1011 molecules of K+ s-5 at rest up to about 15 x 1011 molecules of K+ s-1 during mechanical stimuli. 5. Measurement of intra-ampullar K+ concentration demonstrated that the amount of K+ transported from the perilymph towards the endolymph can be rapidly altered by modifying its perilymphatic levels. This suggests that vestibular organs are endowed with K+ homeostatic mechanisms able to buffer in a very efficient way the concentration of K+ in both the fluids bathing the crista ampullaris.6. The possible role of K+ homeostatic mechanisms in hair cell adaptation is discussed.

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Section: Discussionmentioning

confidence: 99%

Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog.

Valli

Zucca

Botta

1990

The Journal of Physiology

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“…This could be explained by different potassium permeabilities of the plasma membranes of MNL and PMNL. Uncoupled sodium-efflux in MNL may also be considered as a possible mechanism for the decreased uptake of K+ (86Rb+) by MNL (Glynn & Karlish, 1975 , 1984;Clausen, 1986;Ford et al, 1979). Qualitative differences in the pump units from different tissues may also occur.…”

Section: Discussionmentioning

confidence: 99%

Ouabain inhibition of the sodium‐potassium pump: estimation of ED50 in different types of human leucocytes in vitro.

Møller

Vaag

Johansen

1990

Brit J Clinical Pharma

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1. We examined the effect of ouabain on the Na(+)‐K+ pump of intact mononuclear leucocytes and polymorphonuclear leucocytes by using the radioactive potassium analogue, 86rubidium, as a tracer and measuring the cellular uptake of K+ (86Rb+). Na(+)‐K+ pump activity was determined as the cellular uptake of K+ (86Rb+) that is sensitive to ouabain, 10(‐5) mol l‐1. 2. Dose‐response curves for inhibition of the Na(+)‐K+ pump were obtained after exposure of the cells to various concentrations of ouabain for 2.5 h when the level of pump inhibition was considered to be at steady state. 3. The ED50 of ouabain for the effect on the Na(+)‐K+ pump was estimated to be 3 X 10(‐9) mol l‐1 in the absence of potassium. In the presence of potassium, 3 and 6.5 X 10(‐ 3) mol l‐1, it was increased by factors of 10 and 45 respectively. In the presence of potassium, 4 X 10(‐3) mol l‐1, the ED50 was similar but somewhat higher when determined in an artificial medium (Ringer solution) than when determined in autologous plasma. 4. The ED50 values observed in the present study were very similar to KD values reported in the literature on ligand binding of tritiated ouabain to the same types of human leucocytes.

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“…The mechanism of inhibition of the tonic component of contraction by PKC was unrelated to an effect on phosphoinositide hydrolysis (Sasaguri & Watson, 1989a). Na'-K+-ATPase is crucial for the maintenance of ionic gradients across biological membranes (for review, see Glynn & Karlish, 1975;Jorgensen, 1982;Kaplan, 1985) and its activation causes hyperpolarization of the membrane (Bolton, 1973a). This action leads to the relaxation of excitable smooth muscles such as the guinea-pig ileum.…”

Section: Introductionmentioning

confidence: 99%

Phorbol esters inhibit smooth muscle contractions through activation of Na⁺ ‐K⁺ ‐ATPase

Sasaguri

Watson

1990

British J Pharmacology

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1 The role of protein kinase C (PKC) in agonist-induced contractions of guinea-pig ileum longitudinal smooth muscle has been investigated. 2 The phorbol esters, phorbol 12,13-dibutyrate (PDBu), phorbol 12,13-diacetate (PDA) and phorbol 12-myristate 13-acetate (PMA), relaxed tissues precontracted by submaximal concentrations of carbachol, histamine or substance P. 3 This inhibitory action of the phorbol esters was reversed following the application of ouabain, a specific inhibitor of Na'-K+-ATPase. Similarly, pretreatment with ouabain inhibited the ability of phorbol esters to relax tissues precontracted by the above agonists. 4 The slow relaxation of the tonic component of contraction induced by submaximal concentrations of carbachol and histamine, and all concentrations of substance P, was abolished in the presence of ouabain. 5 In Nat-loaded tissues, PDBu and carbachol caused a concentration-dependent increase of Na'-K+-ATPase activity, assessed by ouabain-sensitive 86Rb+-uptake. Extrusion of Nat, assessed by the cellular content of the ion, was also stimulated by PDBu (the effect of carbachol was not investigated). 6 We conclude that phorbol esters inhibit the tonic component of contractions induced by submaximal concentrations of these agonists through activation of Na'-K+-ATPase. We suggest that PKC may exert feedback control over the tonic component of agonist contractions through stimulation of the pump.

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The Sodium Pump

Cited by 866 publications

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Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog.

Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog.

Ouabain inhibition of the sodium‐potassium pump: estimation of ED50 in different types of human leucocytes in vitro.

Phorbol esters inhibit smooth muscle contractions through activation of Na⁺ ‐K⁺ ‐ATPase

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The Sodium Pump

Cited by 866 publications

References 0 publications

Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog.

Perilymphatic potassium changes and potassium homeostasis in isolated semicircular canals of the frog.

Ouabain inhibition of the sodium‐potassium pump: estimation of ED50 in different types of human leucocytes in vitro.

Phorbol esters inhibit smooth muscle contractions through activation of Na+ ‐K+ ‐ATPase

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Phorbol esters inhibit smooth muscle contractions through activation of Na⁺ ‐K⁺ ‐ATPase