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The Journal of physiology1999; 515 ( Pt 2)(Pt 2); 431-437; doi: 10.1111/j.1469-7793.1999.431ac.x

Oxygen-dependent K+ influxes in Mg2+-clamped equine red blood cells.

Abstract: 1. Cl--dependent K+ (86Rb+) influxes were measured in oxygenated and deoxygenated equine red blood cells, whose free [Mg2+]i had been clamped, to examine the effect on O2 dependency of the K+-Cl- cotransporter. 2. Total [Mg2+]i was 2.55 +/- 0.07 mM (mean +/- s.e.m. , n = 6). Free [Mg2+]i was estimated at 0.45 +/- 0.04 and 0.68 +/- 0. 03 mM (mean +/- s.e.m., n = 4) in oxygenated and deoxygenated red cells, respectively. 3. K+-Cl- cotransport was minimal in deoxygenated cells but substantial in oxygenated ones. Cl--dependent K+ influx, inhibited by calyculin A, consistent with mediation via the K+-Cl- cotransporter, was revealed by depleting deoxygenated cells of Mg2+. 4. Decreasing [Mg2+]i stimulated K+ influx, and increasing [Mg2+]i inhibited it, in both oxygenated and deoxygenated red cells. When free [Mg2+]i was clamped, Cl--dependent K+ influxes were always greater in oxygenated cells than in deoxygenated ones, and changes in free [Mg2+]i of the magnitude occurring during oxygenation-deoxygenation cycles had a minimal effect. Physiological fluctuations in free [Mg2+]i are unlikely to provide the primary link coupling activity of the K+-Cl- cotransporter with O2 tension. 5. Volume and H+ ion sensitivity of K+ influx in Mg2+-clamped red cells were increased in O2 compared with those in deoxygenated cells at the same free [Mg2+]i, by about 6- and 2-fold, respectively, but again these features were not responsible for the higher fluxes in oxygenated cells. 6. Regulation of the K+-Cl- cotransporter by O2 is very similar in equine, sheep and in normal human (HbA) red cells, but altered in human sickle cells. Present results imply that, as in sheep red cells, O2 dependence of K+-Cl- cotransport in equine red cells is not mediated via changes in free [Mg2+]i and that cotransport in Mg2+-clamped red cells is still stimulated by O2. This behaviour is contrary to that reported for human sickle (HbS) cells.
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Publication Date: 1999-03-02 PubMed ID: 10050010PubMed Central: PMC2269147DOI: 10.1111/j.1469-7793.1999.431ac.xGoogle Scholar: Lookup
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  • Journal Article
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  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research investigated the effect oxygen dependency has on potassium-chloride cotransport in horse red blood cells, where the free internal concentration of Magnesium ([Mg2+]i) was maintained at a fixed level. The study discussed how oxygenation impacts the activity of the K+ – Cl- cotransporter, and compared how this activity differed in oxygenated versus deoxygenated red blood cells.

The Experiment and Main Findings

  • The experiment involved measuring potassium ion influx in oxygenated and deoxygenated horse red blood cells using radioactivity. The scientists used a technique called “clamping” to keep the concentration of internal Magnesium (Mg2+) – an ion known to influence the cotransporter – constant.
  • The total internal concentration of Magnesium (Mg2+) averaged to be around 2.55 +/- 0.07 mM. The free internal Magnesium concentration in oxygenated cells was lower than in deoxygenated cells.
  • The potassium-chloride cotransporter was found to be minimally active in deoxygenated cells, but clearly active in those cells that had oxygen. When they tried to diminish the Mg2+ concentration of the deoxygenated cells, the potassium influx was inhibited, which suggests the cotransporter mechanism was functioning.

Magnesium’s Effect on the Cotransporter

  • Notably, when they modulated the Magnesium concentration – making it lower, it spurred the K+ influx and in contrast, when Magnesium levels were higher, the potassium influx was inhibited. Despite this, when the concentration of Magnesium in the cells remained constant, the K+ influx was invariably higher in those cells that had oxygen, as opposed to those that didn’t.
  • Meaning, despite physiological changes in internal free Magnesium that happen during cycles of oxygenation and deoxygenation, the effect on the K+-Cl- cotransporter was minor. This implies that the main factor influencing the cotransporter’s activity was not likely to be the Magnesium concentration.

Comparisons with Other Species and Cell Types

  • Greater sensitivity to volume and hydrogen ion levels in cells with oxygen as compared to deoxygenated cells were observed. However, even these factors did not explain the higher potassium influx observed in oxygenated cells.
  • The interaction between the K+-Cl- cotransporter and oxygen concentration measured in this study showed similarities with findings from research conducted on sheep and human red blood cells.
  • Notably, the relationship observed in horse cells was reported to be different from the one in human sickle cells. In sickle cells, unlike in horse and sheep red blood cells, the cotransporter was not stimulated by oxygen, suggesting a unique mechanism in these cells.

Cite This Article

APA
Campbell EH, Cossins AR, Gibson JS. (1999). Oxygen-dependent K+ influxes in Mg2+-clamped equine red blood cells. J Physiol, 515 ( Pt 2)(Pt 2), 431-437. https://doi.org/10.1111/j.1469-7793.1999.431ac.x

Publication

The Journal of physiology
ISSN: 0022-3751
NlmUniqueID: 0266262
Country: England
Language: English
Volume: 515 ( Pt 2)
Issue: Pt 2
Pages: 431-437

Researcher Affiliations

Campbell, E H
  • Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool L69 3BX, UK.
Cossins, A R
    Gibson, J S

      MeSH Terms

      • Animals
      • Calcimycin / pharmacology
      • Carrier Proteins / metabolism
      • Chlorides / physiology
      • Erythrocytes / drug effects
      • Erythrocytes / metabolism
      • Horses / blood
      • Intracellular Membranes / metabolism
      • Magnesium / blood
      • Osmolar Concentration
      • Oxygen / blood
      • Oxygen / physiology
      • Potassium / blood
      • Protons
      • Sodium-Potassium-Chloride Symporters

      Grant Funding

      • Wellcome Trust

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      Citations

      This article has been cited 3 times.
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        doi: 10.1007/s00232-004-0695-6pubmed: 15711773google scholar: lookup
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