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

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 (C57Bl/6J) and a transgenic (alphaHbetaS[betaMDD]) mouse line that expresses high levels of human alphaH and betaS-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 microM 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.

Authors+Show Affiliations

,

Endocrine-Hypertension Division, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA.

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Source

The Journal of membrane biology 159:3 1997 Oct 01 pg 187-96

MeSH

Adult
Anemia, Sickle Cell
Animals
Calcimycin
Calcium-Transporting ATPases
Charybdotoxin
Erythrocytes
Hemoglobin, Sickle
Humans
Ionophores
Mice
Mice, Inbred C57BL
Mice, Transgenic
Potassium
Potassium Channel Blockers
Sodium

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9312208

Citation

Romero, J R., et al. "Red Blood Cells of a Transgenic Mouse Expressing High Levels of Human Hemoglobin S Exhibit Deoxy-stimulated Cation Flux." The Journal of Membrane Biology, vol. 159, no. 3, 1997, pp. 187-96.
Romero JR, Fabry ME, Suzuka S, et al. Red blood cells of a transgenic mouse expressing high levels of human hemoglobin S exhibit deoxy-stimulated cation flux. J Membr Biol. 1997;159(3):187-96.
Romero, J. R., Fabry, M. E., Suzuka, S., Nagel, R. L., & Canessa, M. (1997). Red blood cells of a transgenic mouse expressing high levels of human hemoglobin S exhibit deoxy-stimulated cation flux. The Journal of Membrane Biology, 159(3), pp. 187-96.
Romero JR, et al. Red Blood Cells of a Transgenic Mouse Expressing High Levels of Human Hemoglobin S Exhibit Deoxy-stimulated Cation Flux. J Membr Biol. 1997 Oct 1;159(3):187-96. PubMed PMID: 9312208.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Red blood cells of a transgenic mouse expressing high levels of human hemoglobin S exhibit deoxy-stimulated cation flux. AU - Romero,J R, AU - Fabry,M E, AU - Suzuka,S, AU - Nagel,R L, AU - Canessa,M, PY - 1997/10/6/pubmed PY - 1997/10/6/medline PY - 1997/10/6/entrez SP - 187 EP - 96 JF - The Journal of membrane biology JO - J. Membr. Biol. VL - 159 IS - 3 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 (C57Bl/6J) and a transgenic (alphaHbetaS[betaMDD]) mouse line that expresses high levels of human alphaH and betaS-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 microM 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. SN - 0022-2631 UR - https://www.unboundmedicine.com/medline/citation/9312208/Red_blood_cells_of_a_transgenic_mouse_expressing_high_levels_of_human_hemoglobin_S_exhibit_deoxy_stimulated_cation_flux_ L2 - https://medlineplus.gov/potassium.html DB - PRIME DP - Unbound Medicine ER -