Two functional Na<sup>+</sup>/K<sup>+</sup>‐ATPase isoforms in the left ventricle of guinea pig heart

Berrebi-Bertrand, Isabelle; Maixent, Jean-Michel; Guede, Frederic G.; Gerbi, Alain; Charlemagne, D.; Lelièvre, L.

doi:10.1111/j.1432-1033.1991.tb15795.x

Cited by 22 publications

(11 citation statements)

References 32 publications

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“…We have reported previously guinea pig ventricular myocytes express two functionally distinct Na/K pumps: one with a high affinity for inhibition by dihydro-ouabain (DHO;* 1 M DHO dissociation constant) and the other with a low affinity (100 M DHO dissociation constant; Gao et al, 1995; for review see Mathias et al, 2000). This is consistent with the observations by others (Mogul et al, 1989;Berrebi-Bertrand et al, 1991). We also have reported that mRNA for the ␣ 1 -and ␣ 2 -isoforms of the Na/K ATPase coexist in guinea pig ventricular myocytes (Gao et al, 1999a).…”

supporting

confidence: 89%

Isoform-specific Stimulation of Cardiac Na/K Pumps by Nanomolar Concentrations of Glycosides

Gao

Wymore

Wang

et al. 2002

The Journal of General Physiology

117

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It is well-known that micromolar to millimolar concentrations of cardiac glycosides inhibit Na/K pump activity, however, some early reports suggested nanomolar concentrations of these glycosides stimulate activity. These early reports were based on indirect measurements in multicellular preparations, hence, there was some uncertainty whether ion accumulation/depletion rather than pump stimulation caused the observations. Here, we utilize the whole-cell patch-clamp technique on isolated cardiac myocytes to directly measure Na/K pump current (IP) in conditions that minimize the possibility of ion accumulation/depletion causing the observed effects. In guinea pig ventricular myocytes, nanomolar concentrations of dihydro-ouabain (DHO) caused an outward current that appeared to be due to stimulation of IP because of the following: (1) it was absent in 0 mM [K+]o, as was IP; (2) it was absent in 0 mM [Na+]i, as was IP; (3) at reduced [Na+]i, the outward current was reduced in proportion to the reduction in IP; (4) it was eliminated by intracellular vanadate, as was IP. Our previous work suggested guinea pig ventricular myocytes coexpress the α1- and α2-isoforms of the Na/K pumps. The stimulation of IP appears to be through stimulation of the high glycoside affinity α2-isoform and not the α1-isoform because of the following: (1) regulatory signals that specifically increased activity of the α2-isoform increased the amplitude of the stimulation; (2) regulatory signals that specifically altered the activity of the α1-isoform did not affect the stimulation; (3) changes in [K+]o that affected activity of the α1-isoform, but not the α2-isoform, did not affect the stimulation; (4) myocytes from one group of guinea pigs expressed the α1-isoform but not the α2-isoform, and these myocytes did not show the stimulation. At 10 nM DHO, total IP increased by 35 ± 10% (mean ± SD, n = 18). If one accepts the hypothesis that this increase is due to stimulation of just the α2-isoform, then activity of the α2-isoform increased by 107 ± 30%. In the guinea pig myocytes, nanomolar ouabain as well as DHO stimulated the α2-isoform, but both the stimulatory and inhibitory concentrations of ouabain were ∼10-fold lower than those for DHO. Stimulation of IP by nanomolar DHO was observed in canine atrial and ventricular myocytes, which express the α1- and α3-isoforms of the Na/K pumps, suggesting the other high glycoside affinity isoform (the α3-isoform) also was stimulated by nanomolar concentrations of DHO. Human atrial and ventricular myocytes express all three isoforms, but isoform affinity for glycosides is too similar to separate their activity. Nevertheless, nanomolar DHO caused a stimulation of IP that was very similar to that seen in other species. Thus, in all species studied, nanomolar DHO caused stimulation of IP, and where the contributions of the high glycoside affinity α2- and α3-isoforms could be separated from that of the α1-isoform, it was only the high glycoside affinity isoform that was stimulated. These observations support ear...

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supporting

confidence: 89%

Isoform-specific Stimulation of Cardiac Na/K Pumps by Nanomolar Concentrations of Glycosides

Gao

Wymore

Wang

et al. 2002

The Journal of General Physiology

117

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“…The role of ␣ 3 Na ؉ /K ؉ ATPase in cough receptor function Sodium pump isozymes can be differentiated by their affinity for ouabain (Maixent et al, 1987;Berrebi-Bertrand et al, 1991;Berrebi-Bertrand and Maixent, 1994;Gao et al, 1995;Juhaszova and Blaustein, 1997;Dobretsov et al, 1999;Lingrel et al, 2003). The apparent potency of ouabain for preventing FM2-10 labeling was consistent with the expression of an ␣ 3 -containing isozyme of Na ϩ /K ϩ ATPase in tracheal cough receptors.…”

mentioning

confidence: 67%

Selective Expression of a Sodium Pump Isozyme by Cough Receptors and Evidence for Its Essential Role in Regulating Cough

Mazzone¹,

Reynolds²,

Mori³

et al. 2009

J. Neurosci.

107

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We have identified a distinct subtype of airway vagal afferent nerve that plays an essential role in regulating the cough reflex. These afferents are exquisitely sensitive to punctate mechanical stimuli, acid, and decreases in extracellular chloride concentrations, but are insensitive to capsaicin, bradykinin, histamine, adenosine, serotonin, or changes in airway intraluminal pressures. In this study we used intravital imaging, retrograde neuronal tracing, and electrophysiological analyses to characterize the structural basis for their peculiar mechanical sensitivity and to further characterize the regulation of their excitability. In completing these experiments, we uncovered evidence for an essential role of an isozyme of Na ϩ -K ϩ ATPase in regulating cough. These vagal sensory neurons arise bilaterally from the nodose ganglia and are selectively and brilliantly stained intravitally with the styryl dye FM2-10. Cough receptor terminations are confined and adherent to the extracellular matrix separating the airway epithelium and smooth muscle layers, a site of extensive remodeling in asthma and chronic obstructive pulmonary disease. The cough receptor terminals uniquely express the ␣ 3 subunit of Na ϩ -K ϩ ATPase. Intravital staining of cough receptors by FM2-10, cough receptor excitability in vitro, and coughing in vivo are potently and selectively inhibited by the sodium pump inhibitor ouabain. These data provide the first detailed morphological description of the peripheral terminals of the sensory nerves regulating cough and identify a selective molecular target for their modulation.

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“…Reduction and alkylation of denatured Na+,K+-ATPase has been reported to enhance the electrophoretic separation of the isoforms,34 an observation that we have confirmed for rat brain and heart.32 Reduction and alkylation of guinea pig ventricular Na+,K+-ATPase was reported to cause the a subunit to split into two bands, which were assumed (without more direct evidence) to be al and a2. 33 We attempted to reproduce this. Reduction and alkylation caused an upward shift in the mobility of the Na+,Kt-ATPase a bands as usual ( Fig 10).…”

Section: Other Speciesmentioning

confidence: 99%

Immunologic identification of Na+,K(+)-ATPase isoforms in myocardium. Isoform change in deoxycorticosterone acetate-salt hypertension.

Sweadner

Herrera

Amato

et al. 1994

Circulation Research

115

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There are three isoforms of the catalytic (alpha) subunit of the Na+,K(+)-ATPase, each derived from a different gene, that differ in their sensitivity to inhibition by cardiac glycosides. Antibodies specific for the three isoforms were used to study Na+,K(+)-ATPase isoform expression in ventricular myocardium, where an understanding of digitalis receptor diversity is most important. In the rat heart, there is simultaneous expression of two isoforms in adult ventricle, and immunofluorescence studies demonstrated that both isoforms are expressed uniformly in cardiomyocytes. Hypertension and hypertrophy have been reported to selectively depress alpha 2 isoform mRNA levels, and we show in the present study that alpha 2 protein levels were correspondingly depressed in rats made hypertensive by uninephrectomy and treatment with deoxycorticosterone acetate and a high-salt diet. In the human heart, where mRNA for all three alpha isoforms has been reported, we detected all three isoform proteins (alpha 1, alpha 2, and alpha 3). Two isoforms (alpha 1 and alpha 3) predominated in the macaque heart; dissection of the heart showed uniformity of isoform expression in different ventricular regions but markedly less alpha 3 in the atrium. Finally, isoform-specific antibodies were used to detect which alpha isoforms were expressed in the ventricles of several commonly used experimental animals to test the correlation of isoform expression with cardiac glycoside-response heterogeneity. Two isoforms (alpha 1 and alpha 3) were found in canine myocardium, whereas only one (alpha 1) was found in sheep and guinea pig. Expression of Na+,K(+)-ATPase isoforms can thus be readily followed and related to the physiology of the digitalis receptor.

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Two functional Na⁺/K⁺‐ATPase isoforms in the left ventricle of guinea pig heart

Cited by 22 publications

References 32 publications

Isoform-specific Stimulation of Cardiac Na/K Pumps by Nanomolar Concentrations of Glycosides

Isoform-specific Stimulation of Cardiac Na/K Pumps by Nanomolar Concentrations of Glycosides

Selective Expression of a Sodium Pump Isozyme by Cough Receptors and Evidence for Its Essential Role in Regulating Cough

Immunologic identification of Na+,K(+)-ATPase isoforms in myocardium. Isoform change in deoxycorticosterone acetate-salt hypertension.

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Two functional Na+/K+‐ATPase isoforms in the left ventricle of guinea pig heart

Cited by 22 publications

References 32 publications

Isoform-specific Stimulation of Cardiac Na/K Pumps by Nanomolar Concentrations of Glycosides

Isoform-specific Stimulation of Cardiac Na/K Pumps by Nanomolar Concentrations of Glycosides

Selective Expression of a Sodium Pump Isozyme by Cough Receptors and Evidence for Its Essential Role in Regulating Cough

Immunologic identification of Na+,K(+)-ATPase isoforms in myocardium. Isoform change in deoxycorticosterone acetate-salt hypertension.

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Two functional Na⁺/K⁺‐ATPase isoforms in the left ventricle of guinea pig heart