Volume-stimulated, Cl−-dependent K+ efflux is highly expressed in young human red cells containing normal hemoglobin or HbS

Canessa, Mitzy; Fabry, Mary E.; Blumenfeld, N; Nagel, Ronald L.

doi:10.1007/bf01869416

Cited by 127 publications

(67 citation statements)

References 25 publications

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“…Calculation of the cotransport fluxes measured in fractionated red cells based on a constant cell number (1013) also showed a statistically significant correlation although the slope of the regression line was reduced (r = -0.629; P _< 0.0017; flux [millimoles per 10 t3 cells] = 1.893 -0.013 x MCV). These results are similar to those reported by Chipperfield and Mangat (1986) and Duhm (1987), but differ from those of Canessa et al (1987), who found no consistent differences in bumetanide-sensitive K efflux between fractions of red cells with different density (and presumably MCVs) from donors with reticulocytosis. The basis for this reported difference with the present results is not clear.…”

Section: Characteristics Of Fractionated Red Cellssupporting

confidence: 89%

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

Mairbäurl

Hoffman

1992

The Journal of General Physiology

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This study is concerned with the relationship between the Na/K/CI cotransport system and the steady-state volume (MCV) of red blood cells. Cotransport rate was determined in unfractionated and density-separated red cells of different MCV from different donors to see whether cotransport differences contribute to the difference in the distribution of MCVs. Cotransport, studied in cells at their original MCVs, was determined as the bumetanide (10 ~.M)-sensitive 2~Na efflux in the presence of ouabain (50 I~M) after adjusting cellular Na (Nai) and K~ to achieve near maximal transport rates. This condition was chosen to rule out MCV-related differences in Nai and Ki that might contribute to differences in the net chemical driving force for cotransport. We found that in both unfractionated and density-separated red cells the cotransport rate was inversely correlated with MCV. MCV was correlated directly with red cell 2,3-diphosphoglycerate (DPG), whereas total red cell Mg was only slightly elevated in cells with high MCV. Thus intraceUular free Mg (Mg~ e) is evidently lower in red cells with high 2,3-DPG (i.e., high MCV) and vice versa. Results from flux measurements at their original MCVs, after altering Mg[ r~ with the ionophore A23187, indicated a high Mgi sensitivity of cotransport: depletion of M~ r~ inhibited and an elevation of M~ tee increased the cotransport rate. The apparent K05 for Mg~ e" was ~ 0.4 mM. Maximizing Mig~ ~ at optimum Nai and I~ minimized the differences in cotransport rates among the different donors. It is concluded that the relative cotransport rate is regulated for cells in the steady state at their original cell volume, not by the number of copies of the cotransporter but by differences in Mig~ ~. The interindividual differences in Mg~ ~, determined primarily by differences in the 2,3-DPG content, are responsible for the differences in the relative cotransport activity that results in an inverse Address reprint requests to Dr.

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Section: Characteristics Of Fractionated Red Cellssupporting

confidence: 89%

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

Mairbäurl

Hoffman

1992

The Journal of General Physiology

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“…4 However, Hb S or Hb C in trait RBCs (AS or AC) with normal mean cell age, or after incorporation into normal RBC ghosts, appears to increase KCC activity. 5,6 Expression of Hb S or C in transgenic mice also increases red cell KCC activity.…”

Section: Introductionmentioning

confidence: 99%

“…KCC is active in reticulocytes and diminishes with red cell maturation. 3,4 It is thought to function physiologically to reduce red blood cell (RBC) volume and establish the high cellular hemoglobin concentration (CHC) characteristic of mature cells. KCC is activated in vitro by cell swelling, acid pH, sulfhydryl oxidation/alkylation, and exposure to urea, but the relative importance of these stimuli in vivo is unknown.…”

Section: Introductionmentioning

confidence: 99%

Urea stimulation of KCl cotransport induces abnormal volume reduction in sickle reticulocytes

Joiner

Rettig

Jiang

et al. 2006

Blood

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KCl cotransport (KCC) activity contributes to pathologic dehydration in sickle (SS) red blood cells (RBCs). KCC activation by urea was measured in SS and IntroductionThe KCl cotransporter (KCC) mediates electroneutral coupled transport of K ϩ and Cl Ϫ in a variety of cell types. 1,2 KCC activation results in net efflux of KCl from cells with high potassium content, with accompanying water loss and volume reduction. KCC is active in reticulocytes and diminishes with red cell maturation. 3,4 It is thought to function physiologically to reduce red blood cell (RBC) volume and establish the high cellular hemoglobin concentration (CHC) characteristic of mature cells. KCC is activated in vitro by cell swelling, acid pH, sulfhydryl oxidation/alkylation, and exposure to urea, but the relative importance of these stimuli in vivo is unknown.In RBCs containing sickle hemoglobin (Hb S), KCC activity is high, in part because of the high percentage of reticulocytes. 4 However, Hb S or Hb C in trait RBCs (AS or AC) with normal mean cell age, or after incorporation into normal RBC ghosts, appears to increase KCC activity. 5,6 Expression of Hb S or C in transgenic mice also increases red cell KCC activity. 7 Recently, we demonstrated an abnormal response to acid pH in SS RBCs that was partially corrected by incubation with the sulfhydryl reducing agent, dithiothreitol. 8 These findings suggested that regulation of KCC is abnormal in SS RBCs.As a volume regulator, KCC activity is responsive to CHC. 9,10 KCC is activated on cell swelling, and, as KCl is lost, cell volume falls, cellular hemoglobin concentration increases, and transport activity diminishes. The resultant CHC thus reflects the physiologic "volume set point" of the system. The inactivation of KCC as the cell shrinks toward its new steady state is most likely a key factor in defining the volume regulatory function of the transporter, which in turn is crucial for establishing the steady state CHC for RBCs in vivo.Volume reduction mediated by KCC has been demonstrated with RBC density measurements. 7,11,12 However, these studies, like flux studies, are complicated by varying numbers of reticulocytes (or young cells) in unfractionated SS blood, which preclude comparisons of KCC-mediated volume reduction in SS and AA cells. We recently compared the RVD mediated by KCC and stimulated by cell swelling and acid pH in SS and AA reticulocytes by tracking the changes in reticulocyte CHC by means of density gradient analysis. 8 Acid-stimulated volume reduction was exaggerated in SS reticulocytes and was diminished by sulfhydryl reduction, parallel to the behavior of KCC flux activity. However, despite the normal response of KCC flux activation to cell swelling in SS RBCs, swelling-stimulated volume reduction was markedly abnormal in SS reticulocytes and resulted in higher final CHC than in AA reticulocytes. Thus, volume reduction and KCC fluxes appear to reflect different functional aspects of the KCC system in RBCs and may be subject to different pathologic influences in SS RBCs...

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“…17 The KCC is active in reticulocytes, especially sickle reticulocytes, but not in mature RBCs. 18 This pathway is probably not active in older, dense sickle cells.…”

Section: Introductionmentioning

confidence: 99%

Rehydration of high-density sickle erythrocytes in vitro

Holtzclaw

Jiang

Yasin

et al. 2002

Blood

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Recent studies have identified older, low-density sickle red blood cells (SSRBCs) that were resistant to dehydration by valinomycin, a K ؉ ionophore. These cells, thought to derive from dense SSRBCs that have rehydrated, may represent a terminal cellular phase. To study rehydration, we subjected dense SSRBCs ( > 1.107 g/cc) to either oxygenated incubation or rapid oxygenated/deoxygenated (oxy/deoxy) cycling (70 seconds per cycle). Light cells ( < 1.087 g/cc) were generated during both oxy incubation (2.9% ؎ 2.1%; n ‫؍‬ 42) and oxy/deoxy cycling (5.3% ؎ 2.4%; n ‫؍‬ 42). The rehydrated cells were K ؉ -depleted (K ؉ ‫؍‬ 20 ؎ 14 mmol/kg hemoglobin [Hb]) and Na ؉ -loaded (Na ؉ ‫؍‬ 394 ؎ 106 mmol/kg Hb), and had high levels of external phosphatidylserine. In the presence of external calcium, the generation of rehydrated SSRBCs was inhibited during oxy/deoxy cycling, but the percentage with external phosphatidylserine increased. The calcium-mediated inhibition of rehydration was reversed by charybdotoxin, implying that rehydration was delayed in some cells by the Ca ؉؉ -activated K ؉ channel. Preincubation of dense SSRBCs with DIDS (4,4-di-isothiocyanato-2,2-disulfostilbene) inhibited the generation of light cells during fast oxy/deoxy cycling, but not during oxy incubation. These results suggest that the sickling-induced pathway, previously implicated in SSRBC dehydration, may be involved in the deoxy-dependent component of rehydration for dense, K ؉ -depleted cells. Light-cell generation was inhibited by 1 mM bumetanide during both oxy incubation and oxy/deoxy cycling, providing evidence that a bumetanide-sensitive, deoxy-independent pathway, previously described in circulating light SSRBCs, also contributes to the rehydration of high-density SSRBCs. (Blood. 2002; 100:3017-3025)

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Volume-stimulated, Cl−-dependent K+ efflux is highly expressed in young human red cells containing normal hemoglobin or HbS

Cited by 127 publications

References 25 publications

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

Internal magnesium, 2,3-diphosphoglycerate, and the regulation of the steady-state volume of human red blood cells by the Na/K/2Cl cotransport system.

Urea stimulation of KCl cotransport induces abnormal volume reduction in sickle reticulocytes

Rehydration of high-density sickle erythrocytes in vitro

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