Oxygenation-activated K fluxes in trout red blood cells

Nielsen, Ole Bækgaard; Lykkeboe, Gunnar; Cossins, A. R.

doi:10.1152/ajpcell.1992.263.5.c1057

Cited by 84 publications

(56 citation statements)

References 32 publications

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“…Nevertheless, cells maintained in Nµ exhibited considerable volume sensitivity: the ratio of K¤ influx in swollen cells to that in shrunken cells was 1·83 ± 0·10 (n = 16) in Nµ and 2·35 ± 0·20 (n = 16) in Oµ. In other species (Canessa et al 1987;Borgese et al 1991;Nielsen et al 1992;Honess et al 1996), the volume-sensitive K¤ influx, mediated via the KCl cotransporter, is entirely Oµ dependent. The apparent difference in behaviour of LK sheep red cells was therefore investigated further.…”

Section: Resultsmentioning

confidence: 92%

“…Taken together, these observations are indicative of a role for Oµ-haemoglobin interactions in the mechanism of Oµ dependence of the cotransporter. In both trout and horse, the Cl¦-dependent K¤ influx is abolished in deoxygenated cells (Nielsen et al 1992;Honess et al 1996). This was not the case with LK sheep red cells, in which the Cl¦-dependent K¤ influx in Nµ comprised a substantial component of the residual K¤ influx in deoxygenated cells.…”

Section: Discussionmentioning

confidence: 94%

“…Oµ-sensitive Cl¦-dependent K¤ fluxes have been observed in red cells from a number of different species, including human (Canessa et al 1987), trout (Nielsen et al 1992) and horse (Honess et al 1996). Fluctuations in free [Mg¥]é are widely held to participate in the transduction pathway coupling POµ to activity of the cotransporter (Canessa et al 1987;Apovo et al 1994).…”

Section: Intracellular Magnesium and Oµ Dependency Of K¤ Influxesmentioning

confidence: 99%

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Oxygen‐dependent K⁺ fluxes in sheep red cells

Campbell

Gibson

1998

The Journal of Physiology

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This study was designed to investigate the O2 dependence of K+ influx in sheep red cells. Influx was determined using 86Rb+ as a tracer for K+; glass tonometers coupled to a gas mixing pump were used to equilibrate cell samples to the requisite oxygen tension (PO2). Both volume‐ and H+‐stimulated K+ influxes in low potassium‐containing (LK) sheep red cells were approximately doubled on equilibration with O2 relative to influxes measured in N2. O2‐dependent influxes were abolished when Cl− was replaced with NO3−, consistent with mediation by the KCl cotransporter. At pH 7, PO2 required for half‐maximal stimulation was 56 ± 1 mmHg (mean ± s.e.m., 3 sheep) for the O2‐dependent component of K+ influx: thus PO2 values over the physiological range affected K+ influx. K+ influx in fully deoxygenated sheep red cells showed substantial volume and H+ sensitivity. These residual components in N2 were also Cl− dependent, indicating that the KCl cotransporter of LK sheep red cells was active in the absence of O2. Volume‐sensitive K+ influxes in high potassium‐containing (HK) sheep red cells responded in a similar way to those in cells from LK sheep, although much smaller in magnitude, showing that intracellular [K+] had no significant effect on the O2 dependence of the cotransporter. Intracellular [Mg2+] ([Mg2+]i) was altered by incubating sheep red cells with A23187 (20 μM) and different values of extracellular [Mg2+] ([Mg2+]o). Total [Mg2+]i was determined by atomic absorption spectroscopy and free [Mg2+]i from [Mg2+]o and the Donnan ratio. Total [Mg2+]i was 1.29 ± 0.08 mM (mean ± s.e.m., n= 5), similar to that reported in the literature. Estimates of free [Mg2+]i showed an increase from 0.39 ± 0.05 in oxygenated cells to 0.52 ± 0.04 mM (mean ± s.e.m., n= 5; P < 0.05) in deoxygenated ones. Finally, although K+ influxes were altered by pharmacological loading or depletion of cells with Mg2+, the free [Mg2+]i required to affect influxes significantly was outside the physiological range. Results are difficult to reconcile with PO2 modulating KCl cotransport activity directly via changes in free [Mg2+]i or [Mg2+‐ATP]i.

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Section: Resultsmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 94%

Section: Intracellular Magnesium and Oµ Dependency Of K¤ Influxesmentioning

confidence: 99%

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Oxygen‐dependent K⁺ fluxes in sheep red cells

Campbell

Gibson

1998

The Journal of Physiology

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“…NKCC in turkey: Palfrey & Greengard, 1981; â_NHE in trout: Motais et al 1987;Nikinmaa et al 1987b;and KCC in trout: Borgese et al 1991). The response of KCC to Oµ has been well characterized in trout (Nielsen et al 1992;Cossins et al 1994) and other species (carp: Jensen, 1992; horse: Gibson et al 1993;sheep: Campbell & Gibson, 1998; human HbA and HbS red cells: Gibson et al 1998). Physiological POµ levels activate the cotransporter (Nielsen et al 1992;Honess et al 1996; and are required before it can respond to other stimuli such as swelling, acid or urea.…”

Section: Discussionmentioning

confidence: 99%

Regulation of Na⁺‐K⁺‐2Cl⁻ cotransport in turkey red cells: the role of oxygen tension and protein phosphorylation

Muzyamba¹,

Cossins

Gibson³

1999

The Journal of Physiology

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The ability to regulate cell volume in the face of perturbation is a commonly observed property of cells (Parker, 1993;Hoffmann & Dunham, 1995). Shrinkage in response to an initial increase in volume is termed regulatory volume decrease (RVD); swelling in response to shrinkage is termed regulatory volume increase (RVI). In the short term, RVI and RVD are carried out by a variety of membrane transport systems, which use pre-existing electrochemical gradients for the dissipative movement of a range of solutes (or osmolytes). Water then passively follows these solutes by osmosis. Volume regulatory capacities, together with the identity of the transport systems, vary with cell type and species. This is well illustrated by examining the pattern of volume regulatory responses found in vertebrate red cells (Cossins & Gibson, 1997), whose ease of procurement and homogeneity have made them a popular choice for the study of such processes. Avian red cells possess a powerful Na¤-K¤-2Cl¦ cotransport system (

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“…P O 2 dependency of shrinkage-induced Na influx and RVI Oxygenation-dependent RBC membrane transporters have now been described in nearly all vertebrate classes, ranging from lamprey to mammals (Motais et al, 1987;Nielsen et al, 1992;Gibson et al, 1998;Virkki et al, 1998;Muzyamba et al, 1999;Berenbrink et al, 2000;Berenbrink et al, 2006;Flatman, 2005) (reviewed by Gibson et al, 2000). This also applies to the transporters involved in volume regulation (Jensen, 1995;Nielsen, 1997;Gibson et al, 2000;Brauner et al, 2002;Drew et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Oxygen-sensitive regulatory volume increase and Na transport in red blood cells from the cane toad,Bufo marinus

Kristensen

Koldkjær

Berenbrink

et al. 2007

Journal of Experimental Biology

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SUMMARY The red blood cells (RBCs) of cane toad, Bufo marinus, are only partially saturated with oxygen in most of the circulation due to cardiac shunts that cause desaturation of arterial blood. The present study examines the oxygen dependency of RBC ouabain-insensitive unidirectional Na transport,using 22Na, in control cells and in cells exposed to hyperosmotic shrinkage or the β-adrenergic agonist isoproterenol. Deoxygenation per se induced a slow, but significant Na influx, which was paralleled by a slow increase in RBC volume. Hyperosmotic shrinkage by a calculated 25% activated a robust Na influx that in the first 30 min had a strong PO2 dependency with maximal activation at low PO2 values and a P50of ∼5.5 kPa. This activation was completely abolished by the Na/H exchanger (NHE) inhibitor EIPA (10–4 mol l-1). Hyperosmotic shrinkage is particularly interesting in B. marinus as it withstands considerable elevation in extracellular osmolarity following dehydration. Parallel studies showed that deoxygenated B. marinusRBCs had a much faster regulatory volume increase (RVI) response than air-equilibrated RBCs, reflecting the difference in magnitude of Na influxes at the two PO2 values. The extent of RVI(∼60%) after 90 min, however, was similar under the two conditions,reflecting a more prolonged elevation of the shrinkage-induced Na influx in air-equilibrated RBCs. There were no significant differences in the ability to perform RVI between whole blood cells at a PCO2of 1 and 3 kPa or washed RBCs, and 10–4 mol l-1amiloride reduced the RVI under all conditions, whereas 10–5mol l-1 bumetanide had no effect. Isoproterenol(10–5 mol l-1) induced a significant and prolonged increase in an EIPA-sensitive and bumetanide-insensitive Na influx at low PO2 under iso-osmotic conditions, whilst there was no stimulation by isoproterenol for up to 45 min in air-equilibrated RBCs. The prolonged β-adrenergic activation of the Na influx at low PO2 is distinctly different from the rapid and transient stimulation in teleost RBCs, suggesting significant differences in the signal transduction pathways leading to transporter activation between vertebrate groups.

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Oxygenation-activated K fluxes in trout red blood cells

Cited by 84 publications

References 32 publications

Oxygen‐dependent K⁺ fluxes in sheep red cells

Oxygen‐dependent K⁺ fluxes in sheep red cells

Regulation of Na⁺‐K⁺‐2Cl⁻ cotransport in turkey red cells: the role of oxygen tension and protein phosphorylation

Oxygen-sensitive regulatory volume increase and Na transport in red blood cells from the cane toad,Bufo marinus

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Oxygenation-activated K fluxes in trout red blood cells

Cited by 84 publications

References 32 publications

Oxygen‐dependent K+ fluxes in sheep red cells

Oxygen‐dependent K+ fluxes in sheep red cells

Regulation of Na+‐K+‐2Cl− cotransport in turkey red cells: the role of oxygen tension and protein phosphorylation

Oxygen-sensitive regulatory volume increase and Na transport in red blood cells from the cane toad,Bufo marinus

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Oxygen‐dependent K⁺ fluxes in sheep red cells

Oxygen‐dependent K⁺ fluxes in sheep red cells

Regulation of Na⁺‐K⁺‐2Cl⁻ cotransport in turkey red cells: the role of oxygen tension and protein phosphorylation