High-affinity ouabain binding site and low-dose positive inotropic effect in rat myocardium

Adams, Robert J.; Schwartz, Arnold; G, Grupp; Grupp, Ingrid L.; Lee, Shinwoong; Wallick, Earl T.; Powell, T.; Twist, V. W.; Gathiram, P.

doi:10.1038/296167a0

Cited by 139 publications

(48 citation statements)

References 20 publications

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“…As previously shown for amphibian Na,K-ATPase (21), human Na,K-ATPase ␣ isoforms expressed without ␤ subunits were degraded during the chase period (Fig. 1A, lanes 3-8) and only the newly synthesized, endogenous, oocyte ␣ subunits which are intrinsically stable (26), were immunoprecipitated (com-pare lanes 4,6, and 8 to lanes 1 and 2). On the other hand, co-expression with ␤1 (lanes 9 -14), ␤2, or ␤3 subunits (data not shown) permitted for the formation of stable ␣1, ␣2, and ␣3 isoforms indicating that all 3 human ␤ isoforms can assemble with the 3 human ␣ isoforms.…”

Section: Cellular Expression and Processing Of Human Nakatpase Isozymentioning

confidence: 78%

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Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Crambert¹,

Hasler²,

Beggah³

et al. 2000

Journal of Biological Chemistry

395

378

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Na,K-ATPase plays a crucial role in cellular ion homeostasis and is the pharmacological receptor for digitalis in man. Nine different human Na,K-ATPase isozymes, composed of 3 ␣ and ␤ isoforms, were expressed in Xenopus oocytes and were analyzed for their transport and pharmacological properties. According to ouabain binding and K ؉ -activated pump current measurements, all human isozymes are functional but differ in their turnover rates depending on the ␣ isoform. On the other hand, variations in external K ؉ activation are determined by a cooperative interaction mechanism between ␣ and ␤ isoforms with ␣2-␤2 complexes having the lowest apparent K ؉ affinity. ␣ Isoforms influence the apparent internal Na ؉ affinity in the order ␣1 > ␣2 > ␣3 and the voltage dependence in the order ␣2 > ␣1 > ␣3. All human Na,K-ATPase isozymes have a similar, high affinity for ouabain. However, ␣2-␤ isozymes exhibit more rapid ouabain association as well as dissociation rate constants than ␣1-␤ and ␣3-␤ isozymes. Finally, isoformspecific differences exist in the K ؉ /ouabain antagonism which may protect ␣1 but not ␣2 or ␣3 from digitalis inhibition at physiological K ؉ levels. In conclusion, our study reveals several new functional characteristics of human Na,K-ATPase isozymes which help to better understand their role in ion homeostasis in different tissues and in digitalis action and toxicity.

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Section: Cellular Expression and Processing Of Human Nakatpase Isozymentioning

confidence: 78%

“…4). On the basis of the large differences in ouabain sensitivities between ␣1 isoforms (ouabain-resistant) and ␣2 or ␣3 isoforms (ouabainsensitive) of rat or dog, it was also speculated that "inotropic" and "toxic" isoforms determine digitalis action (6,7).…”

mentioning

confidence: 99%

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Crambert¹,

Hasler²,

Beggah³

et al. 2000

Journal of Biological Chemistry

395

378

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“…In cultured rat astrocytes, 0.1-1.0 M of ouabain inhibits the Na ϩ pump (29) and increases stored Ca 2ϩ (V. Golovina and M.P.B., unpublished work). These ouabain concentrations are at least 100-fold below the IC 50 for inhibition of rat ␣1 (1,6,29,30). Thus, we infer that the PM must contain functional ␣2 (astrocytes) or ␣3 (myocytes) subunits.…”

Section: Resultsmentioning

confidence: 99%

Na ⁺ pump low and high ouabain affinity α subunit isoforms are differently distributed in cells

Juhaszova

Blaustein

1997

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

280

246

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Three isoforms (␣1, ␣2, and ␣3) of the catalytic (␣) subunit of the plasma membrane (PM) Na ؉ pump have been identified in the tissues of birds and mammals. These isoforms differ in their affinities for ions and for the Na ؉ pump inhibitor, ouabain. In the rat, ␣1 has an unusually low affinity for ouabain. The PM of most rat cells contains both low (␣1) and high (␣2 or ␣3) ouabain affinity isoforms, but precise localization of specific isoforms, and their functional significance, are unknown. We employed high resolution immunocytochemical techniques to localize ␣ subunit isoforms in primary cultured rat astrocytes, neurons, and arterial myocytes. Isoform ␣1 was ubiquitously distributed over the surfaces of these cells. In contrast, high ouabain affinity isoforms (␣2 in astrocytes, ␣3 in neurons and myocytes) were confined to a reticular distribution within the PM that paralleled underlying endoplasmic or sarcoplasmic reticulum. This distribution is identical to that of the PM Na͞Ca exchanger. This raises the possibility that ␣1 may regulate bulk cytosolic Na ؉ , whereas ␣2 and ␣3 may regulate Na ؉ and, indirectly, Ca 2؉ in a restricted cytosolic space between the PM and reticulum. The high ouabain affinity Na ؉ pumps may thereby modulate reticulum Ca 2؉ content and Ca 2؉ signaling.

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“…There were distinguished two components of 22 Na efflux: ouabain sensitive (Na + /K + pump) and ouabain non sensitive (Na + /Ca 2+ exchange) components. Our work performed on whole (non-perfused) and preliminary 22 Na enriched snail neurones has shown that ouabain high concentration (>10 -7 M) has inhibitory effect on 22 Na efflux as in axon, but its lower concentrations (<10 -7 M) have activation effect on 22 Na efflux [4], which is due to the activation of Na + /Ca 2+ exchange in reverse mode [39]. It is obvious that such differences of ouabain sensitivity of Na + /Ca 2+ exchange in internally perfused squid axon and whole snail neuron can be explained by different membrane properties of squid axon and snail neuronal membrane or by ouabain-induced changes of Ca ions' gradient on Figure 5) and 45 …”

Section: Camentioning

confidence: 99%

“…They also have a different localization in cells: α 1 is ubiquitously distributed over the surfaces of cells, while high ouabain affinity isoforms are confined to a reticular distribution within the cellular membrane that paralleled underlying endoplasmic or sarcoplasmic reticulum, with Na + /Ca 2+ exchanger protein. The expression of these isoforms is age-dependent [20][21][22][23][24][25]. While the role of low-affinity receptors as a working molecule for Na + /K + pump is well established [25][26][27], the functional role of high-affinity receptors is still discussable [13].…”

Section: Introductionmentioning

confidence: 99%

Age-Dependent Brain Tissue Hydration, Ca Exchange and their Dose- Dependent Ouabain Sensitivity

Ayrapetyan¹

2012

JBB

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High-affinity ouabain binding site and low-dose positive inotropic effect in rat myocardium

Cited by 139 publications

References 20 publications

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Na ⁺ pump low and high ouabain affinity α subunit isoforms are differently distributed in cells

Age-Dependent Brain Tissue Hydration, Ca Exchange and their Dose- Dependent Ouabain Sensitivity

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High-affinity ouabain binding site and low-dose positive inotropic effect in rat myocardium

Cited by 139 publications

References 20 publications

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Na + pump low and high ouabain affinity α subunit isoforms are differently distributed in cells

Age-Dependent Brain Tissue Hydration, Ca Exchange and their Dose- Dependent Ouabain Sensitivity

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Na ⁺ pump low and high ouabain affinity α subunit isoforms are differently distributed in cells