Red blood cells of a transgenic mouse expressing high levels of human hemoglobins exhibit deoxy-stimulated cation flux

J. R. Romero, M. E. Fabry, S. Suzuka, R. L. Nagel, M. Canessa

Research output: Contribution to journalArticle

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Abstract

Deoxy-stimulated cation fluxes have been implicated in the generation of the dense and irreversibly sickled red blood cells (RBCs) in patients homozygous for hemoglobin S (SS). We now report on the effect of short term deoxygenation on K+ and Na+ transport in RBCs from control mice (C57B1/6J) and a transgenic (α(H)β(S)[β(MDD)]) mouse line that expresses high levels of human α(H) and β(S)-chains and has a small percent dense cells but does not exhibit anemia. In transgenic mouse RBCs (n = 5) under oxygenated conditions, K+ efflux was 0.22 ± 0.01 mmol/L cell x min and Na+ influx was 0.17 ± 0.02 mmol/L cell x min. Both fluxes were stimulated by 10 min deoxygenation in transgenic but not in control mice. The deoxy-stimulated K+ efflux from transgenic mouse RBCs was about 55% inhibited by 5 nM charybdotoxin (CTX), a blocker of the calcium activated K+-channel. To compare the fluxes between human and mouse RBCs, we measured the area of mouse RBCs and normalized values to area per liter of cells. The deoxy-simulated CTX-sensitive K+ efflux was larger than the CTX-sensitive K+ efflux observed in RBCs from SS patients. These results suggest that in transgenic mice, deoxygenation increases cytosolic Ca2+ to levels which open Ca2+-activated K+ channels. The presence of these channels was confirmed in both control and transgenic mice by clamping intracellular Ca2+ at 10 μM with the ionophore A23187 and measuring Ca2+ activated K+ efflux. Both types of mouse had similar maximal rates of CTX-sensitive, Ca2+-activated K+ efflux that were similar to those in human SS cells. The capacity of the mouse red cell membrane to regulate cytosolic Ca2+ levels was examined by measurements of the maximal rate of calmodulin activated Ca2+-ATPase activity. This activity was 3-fold greater than that observed in human RBCs thus indicating that mouse RBC membranes have more capacity to regulate cytosolic Ca2+ levels. In summary, transgenic mouse RBCs exhibit larger values of deoxy-stimulated K+ efflux and Na+ influx when compared to human SS cells. They have a similar Ca2+-activated K+ channel activity to human SS cells while expressing a very high Ca2+ pump activity. These properties may contribute to the smaller percent of very dense cells and to the lack of adult anemia in this animal model.

Original languageEnglish (US)
Pages (from-to)187-196
Number of pages10
JournalJournal of Membrane Biology
Volume159
Issue number3
DOIs
StatePublished - 1997

Fingerprint

Transgenic Mice
Cations
Hemoglobins
Erythrocytes
Charybdotoxin
Calcium-Activated Potassium Channels
Sickle Hemoglobin
Anemia
Cell Membrane
Calcium-Transporting ATPases
Ionophores
Calcimycin
Calmodulin
Constriction
Human Activities
Animal Models

Keywords

  • Calcium pump
  • Cation transport
  • Erythrocytes
  • Sickle cell anemia
  • Volume regulation

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

Cite this

Red blood cells of a transgenic mouse expressing high levels of human hemoglobins exhibit deoxy-stimulated cation flux. / Romero, J. R.; Fabry, M. E.; Suzuka, S.; Nagel, R. L.; Canessa, M.

In: Journal of Membrane Biology, Vol. 159, No. 3, 1997, p. 187-196.

Research output: Contribution to journalArticle

Romero, J. R. ; Fabry, M. E. ; Suzuka, S. ; Nagel, R. L. ; Canessa, M. / Red blood cells of a transgenic mouse expressing high levels of human hemoglobins exhibit deoxy-stimulated cation flux. In: Journal of Membrane Biology. 1997 ; Vol. 159, No. 3. pp. 187-196.
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abstract = "Deoxy-stimulated cation fluxes have been implicated in the generation of the dense and irreversibly sickled red blood cells (RBCs) in patients homozygous for hemoglobin S (SS). We now report on the effect of short term deoxygenation on K+ and Na+ transport in RBCs from control mice (C57B1/6J) and a transgenic (α(H)β(S)[β(MDD)]) mouse line that expresses high levels of human α(H) and β(S)-chains and has a small percent dense cells but does not exhibit anemia. In transgenic mouse RBCs (n = 5) under oxygenated conditions, K+ efflux was 0.22 ± 0.01 mmol/L cell x min and Na+ influx was 0.17 ± 0.02 mmol/L cell x min. Both fluxes were stimulated by 10 min deoxygenation in transgenic but not in control mice. The deoxy-stimulated K+ efflux from transgenic mouse RBCs was about 55{\%} inhibited by 5 nM charybdotoxin (CTX), a blocker of the calcium activated K+-channel. To compare the fluxes between human and mouse RBCs, we measured the area of mouse RBCs and normalized values to area per liter of cells. The deoxy-simulated CTX-sensitive K+ efflux was larger than the CTX-sensitive K+ efflux observed in RBCs from SS patients. These results suggest that in transgenic mice, deoxygenation increases cytosolic Ca2+ to levels which open Ca2+-activated K+ channels. The presence of these channels was confirmed in both control and transgenic mice by clamping intracellular Ca2+ at 10 μM with the ionophore A23187 and measuring Ca2+ activated K+ efflux. Both types of mouse had similar maximal rates of CTX-sensitive, Ca2+-activated K+ efflux that were similar to those in human SS cells. The capacity of the mouse red cell membrane to regulate cytosolic Ca2+ levels was examined by measurements of the maximal rate of calmodulin activated Ca2+-ATPase activity. This activity was 3-fold greater than that observed in human RBCs thus indicating that mouse RBC membranes have more capacity to regulate cytosolic Ca2+ levels. In summary, transgenic mouse RBCs exhibit larger values of deoxy-stimulated K+ efflux and Na+ influx when compared to human SS cells. They have a similar Ca2+-activated K+ channel activity to human SS cells while expressing a very high Ca2+ pump activity. These properties may contribute to the smaller percent of very dense cells and to the lack of adult anemia in this animal model.",
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AU - Romero, J. R.

AU - Fabry, M. E.

AU - Suzuka, S.

AU - Nagel, R. L.

AU - Canessa, M.

PY - 1997

Y1 - 1997

N2 - Deoxy-stimulated cation fluxes have been implicated in the generation of the dense and irreversibly sickled red blood cells (RBCs) in patients homozygous for hemoglobin S (SS). We now report on the effect of short term deoxygenation on K+ and Na+ transport in RBCs from control mice (C57B1/6J) and a transgenic (α(H)β(S)[β(MDD)]) mouse line that expresses high levels of human α(H) and β(S)-chains and has a small percent dense cells but does not exhibit anemia. In transgenic mouse RBCs (n = 5) under oxygenated conditions, K+ efflux was 0.22 ± 0.01 mmol/L cell x min and Na+ influx was 0.17 ± 0.02 mmol/L cell x min. Both fluxes were stimulated by 10 min deoxygenation in transgenic but not in control mice. The deoxy-stimulated K+ efflux from transgenic mouse RBCs was about 55% inhibited by 5 nM charybdotoxin (CTX), a blocker of the calcium activated K+-channel. To compare the fluxes between human and mouse RBCs, we measured the area of mouse RBCs and normalized values to area per liter of cells. The deoxy-simulated CTX-sensitive K+ efflux was larger than the CTX-sensitive K+ efflux observed in RBCs from SS patients. These results suggest that in transgenic mice, deoxygenation increases cytosolic Ca2+ to levels which open Ca2+-activated K+ channels. The presence of these channels was confirmed in both control and transgenic mice by clamping intracellular Ca2+ at 10 μM with the ionophore A23187 and measuring Ca2+ activated K+ efflux. Both types of mouse had similar maximal rates of CTX-sensitive, Ca2+-activated K+ efflux that were similar to those in human SS cells. The capacity of the mouse red cell membrane to regulate cytosolic Ca2+ levels was examined by measurements of the maximal rate of calmodulin activated Ca2+-ATPase activity. This activity was 3-fold greater than that observed in human RBCs thus indicating that mouse RBC membranes have more capacity to regulate cytosolic Ca2+ levels. In summary, transgenic mouse RBCs exhibit larger values of deoxy-stimulated K+ efflux and Na+ influx when compared to human SS cells. They have a similar Ca2+-activated K+ channel activity to human SS cells while expressing a very high Ca2+ pump activity. These properties may contribute to the smaller percent of very dense cells and to the lack of adult anemia in this animal model.

AB - Deoxy-stimulated cation fluxes have been implicated in the generation of the dense and irreversibly sickled red blood cells (RBCs) in patients homozygous for hemoglobin S (SS). We now report on the effect of short term deoxygenation on K+ and Na+ transport in RBCs from control mice (C57B1/6J) and a transgenic (α(H)β(S)[β(MDD)]) mouse line that expresses high levels of human α(H) and β(S)-chains and has a small percent dense cells but does not exhibit anemia. In transgenic mouse RBCs (n = 5) under oxygenated conditions, K+ efflux was 0.22 ± 0.01 mmol/L cell x min and Na+ influx was 0.17 ± 0.02 mmol/L cell x min. Both fluxes were stimulated by 10 min deoxygenation in transgenic but not in control mice. The deoxy-stimulated K+ efflux from transgenic mouse RBCs was about 55% inhibited by 5 nM charybdotoxin (CTX), a blocker of the calcium activated K+-channel. To compare the fluxes between human and mouse RBCs, we measured the area of mouse RBCs and normalized values to area per liter of cells. The deoxy-simulated CTX-sensitive K+ efflux was larger than the CTX-sensitive K+ efflux observed in RBCs from SS patients. These results suggest that in transgenic mice, deoxygenation increases cytosolic Ca2+ to levels which open Ca2+-activated K+ channels. The presence of these channels was confirmed in both control and transgenic mice by clamping intracellular Ca2+ at 10 μM with the ionophore A23187 and measuring Ca2+ activated K+ efflux. Both types of mouse had similar maximal rates of CTX-sensitive, Ca2+-activated K+ efflux that were similar to those in human SS cells. The capacity of the mouse red cell membrane to regulate cytosolic Ca2+ levels was examined by measurements of the maximal rate of calmodulin activated Ca2+-ATPase activity. This activity was 3-fold greater than that observed in human RBCs thus indicating that mouse RBC membranes have more capacity to regulate cytosolic Ca2+ levels. In summary, transgenic mouse RBCs exhibit larger values of deoxy-stimulated K+ efflux and Na+ influx when compared to human SS cells. They have a similar Ca2+-activated K+ channel activity to human SS cells while expressing a very high Ca2+ pump activity. These properties may contribute to the smaller percent of very dense cells and to the lack of adult anemia in this animal model.

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