Hemoglobin variants and activity of the (K+Cl-) cotransport system in human erythrocytes.

To determine if the activation of the (K+Cl-) cotransport system observed in hemoglobin (Hb) S- or C-containing erythrocytes is related either to a global change of isoelectric point of the Hb molecule or to the specific location of these mutations on the position 6 of the beta chain of Hb, we studied the (K+Cl-) cotransport system in erythrocytes containing beta chain variants exhibiting either the Glu----Lys substitution observed in position beta 6 in Hb C (Hb E: beta 26 Glu----Lys; Hb O-Arab: beta 121 Glu----Lys; Hb Siriraj:beta 7 Glu----Lys) or the Glu----neutral residue substitution observed in position beta 6 in Hb S (Hb G-San Jose: beta 7 Glu----Gly; Hb D Punjab or D-Los Angeles: beta 121 Glu----Gln). The K transport mediated by the (K+Cl-) cotransport was increased in AC, AS and A-Siriraj and A-San Jose red blood cells and was similar to AA control in the other variants. These results indicate that an enhanced (K+Cl-) cotransport is not a property of all positively charged Hb variants, but it is mainly associated with mutations occurring at the beta 6 or beta 7 residues. An interaction of Hb with the cell membrane mediated by the disappearance of one of the negative charged residues (Glu) at this site of the A helix of the beta chain is the most likely candidate for the persistent activation of the (K+Cl-) cotransport system in these Hb variants.     

Red cell membrane Na+ transport systems in hereditary spherocytosis: relevance to understanding the increased Na+ permeability

Red blood cells (RBCs) in hereditary spherocytosis (HS) show high sodium (Na+) and potassium (K+) movement across the membrane, resulting in dehydration. In general, these abnormal cation fluxes have been interpreted as "increased leaks" due to passive or electrodiffusional permeability of the RBC membrane. A study to elucidate the contribution of concomitant ouabain-resistant pathways (Na-K-2Cl cotransport and Na-Li countertransport) to abnormal Na+ permeability present in RBCs of subjects with HS has been undertaken. Accordingly, erythrocyte Na+ and K+ content and transmembrane cation movements via the Na-K pump, Na-K-2Cl cotransport, Na-Li countertransport, and Na+ passive diffusion, were measured in 25 non-splenectomized patients with HS and compared with the results obtained from the study of 11 patients with congenital non-spherocytic haemolytic anaemia (CNSHA) due to hereditary elliptocytosis (7 cases) and RBC enzyme defects (4 cases) and of 30 normal controls. Compared to the controls, patients with HS exhibited a highly significant (P<0.001) increase in all the Na+ transmembrane movements via passive diffusion (411+/-243 vs 105+/-40), Na-K pump (2615+/-970 vs 1874+/-359), Na-K-2Cl cotransport (males: 371+/-138 vs 190+/-42; females: 401+/-134 vs 104+/-44) and Na-Li countertransport (207+/-131 vs 98+/-41). This was associated with increased Na+ and decreased K+ content, resulting in a reduction of total cation (Na+ + K+) RBC concentration. Furthermore, significant correlations were also found between the patients' RBC cationic content and the mean corpuscular haemoglobin concentration (MCHC) (r=0.51, P<0.05) and between the Na+ passive leak and the haematocrit value (r=-0.44, P<0.05). In the patients with CNSHA, a less significant (P<0.01) increase of active (Na-K pump) and passive (leak) transmembrane permeability to Na+ was associated with normal transmembrane movements via Na-K-2Cl cotransport and Na-Li countertransport. The present study demonstrates that in HS, RBCs are characterized by a variable, but always significant increase of all the membrane transport systems leading to the extrusion of Na+, and that these abnormalities, regardless of their relation to membrane structural defects, may probably be valuable for the differential diagnosis between HS and other congenital defects of RBCs.     

Membrane cation and anion transport activities in erythrocytes of hereditary spherocytosis: Effects of different membrane protein defects

Hereditary spherocytosis (HS) is due to different membrane protein defects (i.e., deficiency of spectrin and ankyrin, band 3, or band 4.2). In order to gain new insight into the relationships between band 3 function and proteins associated with the cytoskeleton, we studied erythrocyte anion transport activity in HS characterized by different membrane protein defects. Anion transport activity was increased in HS due to partial band 4.2 deficiency or to band 4.2 absence, while in HS associated with deficiency of spectrin + ankyrin or band 3, the anion transport results were normal or decreased, respectively. Moreover, since HS erythrocytes are characterized by an increased Na and a decreased K, we studied the principal membrane cation transport pathways. Activity of the Na/K pump was increased in all HS studied, while no changes in Na/K/2Cl cotransport and Na/Li exchange were evident between control and HS as well as between forms of HS associated with different membrane protein defects. K/Cl cotransport activity was decreased in all HS studied compared to normal red cells. In all HS, passive membrane permeability to Na and K was increased compared to normal erythrocytes. The increased Na and the low K content can be attributed to the abnormal membrane permeability to cations, which is not related to a specific membrane protein defect. Am. J. Hematol. 55:121–128, 1997. © 1997 Wiley-Liss, Inc.     

Membrane properties of erythrocytes in subjects undergoing multiple blood donations with or without recombinant erythropoietin

Summary. To examine the characteristics of 'young'human red cells, we studied blood from seven healthy male volunteers who developed systemic reticulocytosis during a 3-week blood donation period. Each of these subjects donated a total of 6 units (450 ml/unit) of blood (2 units/week for 3 weeks) with subcutaneous recombinant erythropoietin (SC rEPO; 200 U/kg daily for 3 weeks). Two of these subjects were also studied with a similar protocol in the absence of rEPO (4 · 5 · 0 · 5 units donated). SC rEPO administration was associated with an increased K content of the erythrocyte and with the appearance of hypochromic cells, which were initially normocytic and then became normochromic and microcytic. Measurements of cation transport revealed that, with the exception of the Na-K-Cl cotransport, all the systems studied increased their activities following blood donations with or without SC rEPO. The increase was highest in the K-Cl cotransport (2- and 5-fold for control and rEPO parts of the study, respectively), while the Na-K pump increased slightly in control and 40% with rEPO. The Na-Li countertransport increased 40% and 100% in the control and rEPO parts of the study, respectively. Concomitant with increased ion transport activity, electron microscopic studies of plasma and red cells of subjects receiving SC rEPO showed the presence of circulating exosomes and cytoplasmic multivesicular bodies. The transferrin receptor was detected in the circulating exosomes, thereby providing evidence that, as do nonhuman red cells, maturing human reticulocytes shed exosome-associated transferrin receptors.     

Volume-sensitive K-Cl cotransport in inside-out vesicles made from erythrocyte membranes from sheep of low-K phenotype.

Unidirectional K ion effluxes were measured from inside-out vesicles prepared from erythrocyte membranes from sheep of the low-K phenotype. Total K efflux was 150 nmol per mg of protein per hr in a Cl medium of 295 mosmol/kg (with the Na/K pump inhibited). Cl-dependent K efflux (determined with methanesulfonate replacing Cl) was 54 nmol/(mg.hr). Cl-dependent K efflux (K-Cl cotransport) increased to 77 nmol/(mg.hr) with osmotic swelling of approximately 30% in 230-mosmol/kg medium and decreased to 13 nmol/(mg.hr) after shrinkage of approximately 60% in 430-mosmol/kg medium. Osmotically induced changes in transport and vesicle volume were reversible. K-Cl cotransport was enhanced by ATP. Nonhydrolyzable ATP analogues failed to substitute for ATP, indicating that phosphorylation is involved. However, in the absence of added ATP there was significant K-Cl cotransport, suggesting that phosphorylation is not essential for function. The results provide clues about the nature of the signals detected by the sensor of cell volume changes and demonstrate that inside-out vesicles from sheep erythrocyte membranes provide an advantageous experimental system for investigation of the volume sensor.     

Green tea extract and aged garlic extract inhibit anion transport and sickle cell dehydration in vitro

Both green tea extract (GTE or tea polyphenols) and aged garlic extract (AGE) effectively inhibited in vitro dehydration of sickle red blood cells induced by K-Cl cotransport or red cell storage. For K-Cl cotransport induced by 500 mM urea, 0.3 mg/ml EGCg (epigallocatechin gallate; a major component in GTE) almost completely inhibited dehydration, and 6 mg/ml AGE inhibited dehydration to 30% of the control level. Both vitamins E and C had no effect at the level of 2 mM. Different tea extracts had different degrees of inhibition, but the inhibitory activity increased when the number of hydroxyl groups in the compounds increased. With storage of sickle cells at 4 degrees C for 6 days, the cells started to undergo spontaneous dehydration when incubated at 37 degrees C. Neither inhibitors for Ca-induced K efflux nor K-Cl cotransport could inhibit cell dehydration of stored sickle cells, but both GTE and AGE effectively inhibited it. Chloride efflux measurements using a chloride electrode demonstrated that both GTE and AGE inhibited anion transport in red blood cells. The inhibitory mechanism of these compounds may be related to anion transport inhibition, although involvement of their antioxidant activities can not yet be ruled out.     

Disturbances in Na+ Transport Systems Induced by Ethanol in Human Red Blood Cells

The effects of ethanol on fluxes catalyzed by four Na+ transport systems (ouabain-sensitive Na+, K+ pump, bumetanide-sensitive Na+, K+ cotransport system, Na+:Li+- countertransport and anion carrier) and on Na+ and K+ leaks were investigated in human red blood cells. Ethanol concentrations higher than 32 mM were required in order to significantly modify erythrocyte Na+ transport function. The observed changes can be summarized as follows: (a) stimulation of Na+ efflux through the Na+, K+ pump (by 21-32% at 160-400 mM) and Na+:Li+ countertransport (by 34-59% at 160-400 mM); (b) inhibition of outward Na+, K+ cotransport (by 23-34% at 160-400 mM) and LiCO3- influx through the anion carrier (by 17-21% at 64-400 mM); and (c) increase in Na+ and K+ leaks (by 13-16% at 64-400 mM). The effects of ethanol on the Na+,K+ pump and Na+,K+ cotransport system resulted from changes in maximal rates of Na+ efflux (increased and decreased, respectively) without any significant effect on the apparent affinities for internal Na+. Erythrocytes preincubated for 1 hr with 160 mM ethanol, washed and further incubated in flux media, recovered a normal Na+ transport function. In conclusion, high concentrations of ethanol induced reversible perturbations of fluxes catalyzed by erythrocyte Na+ transport systems. The observed effects may reflect disturbances in Na+ transport function associated with severe intoxication.     

Sodium transport kinetics in erythrocytes and inside-out vesicles from Milan rats.

This paper describes the kinetics of the Na(+)-K+ pump and the Na(+)-K(+)-Cl- cotransport in sodium-loaded erythrocytes and of the Na(+)-K(+)-Cl- cotransport in erythrocyte inside-out vesicles (IOV) from Milan hypertensive (MHS) and normotensive (MNS) rats in order to evaluate the possible role of intracellular factor(s). In intact erythrocytes, no difference was detectable in the Na(+)-K+ pump kinetics between the two strains while the apparent affinity (Km) of Na(+)-K(+)-Cl- cotransport for internal sodium was significantly greater and the maximal rate of sodium transport lower in MHS when compared with MNS rats. IOV, which are depleted of cytoskeleton, showed a bumetanide-sensitive potassium- and chloride-dependent sodium uptake. However, the erythrocyte differences in Na(+)-K(+)-Cl- cotransport activity and the Km between strains disappeared in IOV, suggesting tha the altered sodium transport of MHS erythrocyte might be due to some intracellular factor or a membrane skeleton protein abnormality.     

Heterogeneity of the erythrocyte Na-K pump status in human obesity

The number of Na-K pump units, the Na-K-ATPase activity, the K transport turnover rate per pump unit and the intracellular Na and K concentrations were measured in the erythrocytes of 56 obese patients and 20 normal subjects. No differences were found between the two groups. In obese patients, we failed to observe any influence of dietary habits, age of onset, or family history of obesity on the Na pump status. On the other hand, we found that the number of pump units was not a close reflection of the membrane cation transport and in some patients with an abnormally high number of pump units, an inappropriately low Na-K-ATPase activity was observed. We also identified two small groups of obese patients with, respectively, abnormally high or low K transport turnover rate per pump unit. Our study seems to support the hypothesis that abnormalities in the erythrocyte Na-K pump system are not usual in the obese population but are probably present only in a limited number of selected patients.     

Kinetic analysis of erythrocyte Na+-K+ pump and cotransport in essential hypertension

Alterations in red blood cell (RBC) Na+-K+ pump and Na+-K+ cotransport have been described in essential hypertension. We evaluated Na+-K+ pump and cotransport in 30 hypertensive and 26 normotensive subjects subdivided by race and family history of hypertension using an improved method to examine the kinetics of Na and K effluxes. RBCs were Na-loaded by the nystatin method to five different levels of internal Na with pump determined as ouabain-sensitive Na efflux and cotransport as furosemide-sensitive Na and K efflux. Two kinetic parameters were determined for both transport systems: the apparent affinity for Na (K0.5) and the velocity of efflux at saturating internal Na concentration (Vmax). Mean intracellular Na content in fresh RBCs (mmol/L cells) was higher in black hypertensive (12.6 +/- 1.8 mmol/L cells) and normotensive subjects (10.9 +/- 1.2 mmol/L cells) than in white hypertensive (8.7 +/- 1.0 mmol/L cells) or normotensive subjects (8.5 +/- 0.8 mmol/L cells). The Vmax and K0.5 for pump were not significantly different between study groups. The Vmax for cotransport was elevated in white hypertensive compared with normotensive subjects, but the K0.5 values were similar. Black normotensive and hypertensive subjects displayed a lower Vmax and increased K0.5 for cotransport compared with the white groups. A family history of hypertension had no influence on cotransport kinetics in blacks but did predict white normotensive and hypertensive subjects with low cotransport. The reduction in intracellular Na affinity for cotransport in black subjects may explain their higher intracellular Na in fresh RBCs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Decreased alpha globine mRNA in nucleated red cell precursors in alpha thalassemia.

The alpha thalassemias are associated with a decrease in alpha chain synthesis. Hemoglobin H (HbH) disease is a moderately severe form of alpha thalassemia characterized by the production of 5%--20% of HbH, while alpha thalassemia trait is a milder form of alpha thalassemia. In two patients with HbH disease, the ratio of alpha chain synthesis to beta chain synthesis (alpha/beta ratio) was decreased in both bone marrow cells and reticulocytes. When isolated mRNA from bone marrow cells and reticulocytes was translated in a heterologous cell-free system, the alpha/beta ratios were lower than the intact cell ratios. These findings were confirmed by hybridization of the mRNA of both marrow cells and reticulocytes using purified alpha and beta cDNA probes. In the intact cells of two patients with alpha thalassemia trait, the alpha/beta ratios were also decreased and were similar in marrow cells and reticulocytes. Cell-free studies of translatable mRNA also demonstrated decreased alpha/beta ratios, but, unlike the HbH studies, the cell-free alpha/beta ratios were similar to the intact cell ratios. One hybridization study utilizing peripheral blood mRNA had an alpha/beta ratio consistent with the cell-free ratios. These results indicated that, in both HbH disease and alpha thalassemia trait, there was decreased alpha globin mRNA present in both nucleated red cell precursors and reticulocytes. In addition, the data suggested that there may be translational mechanisms that operate in intact HbH cells which attempt to balance globin chain production. In alpha thalassemia trait cells, no such controls appeared to be active and globin chain synthesis was directly proportional to the amount of alpha and beta globin mRNA in the cells.     

Expression of HbC and HbS, but not HbA, results in activation of K-Cl cotransport activity in transgenic mouse red cells

Elevation of K-Cl cotransport in patients with homozygous hemoglobin (Hb) S or HbC increases red cell mean corpuscular hemoglobin concentration (MCHC) and contributes significantly to pathology. Elucidation of the origin of elevated K-Cl cotransport in red cells with mutant hemoglobins has been confounded by the concomitant presence of reticulocytes with high K-Cl cotransport. In red cells of control mice (C57BL), transgenic mice that express only human HbA, and transgenic mice that express both mouse globins and human HbS, volume stimulation is weak and insensitive to NO3- and dihydroindenyl-oxy-alkanoic acid (DIOA). DIOA and NO3- are inhibitors in all other mammalian red cells. In contrast, in knock-out mice expressing exclusively human hemoglobin HbC or HbS+ gamma, replacement of isotonic Cl- media by hypotonic Cl- resulted in strong volume stimulation and sensitivity to DIOA, okadaic acid, and NO3-. In summary, we find that HbC, under all conditions, and HbS+ gamma, in the absence of mouse globins, have significant quantitative and qualitative effects on K-Cl cotransport in mouse red cells and activate mouse K-Cl. We conclude that human globins are able to stimulate the activity and/or regulation of K-Cl cotransport in mouse red cells. These observations support the contention that HbS and HbC stimulate K-Cl cotransport in human red cells.     

Erythrocyte membrane lipids and cationic transport systems in men.

OBJECTIVE: The relationship between erythrocyte membrane and plasma lipids and various transmembrane erythrocyte cationic fluxes was examined in 53 normal men. DESIGN: Different measurements of erythrocyte transport systems were obtained: Na(+)-Li+ countertransport activity; Na+, K+ cotransport activity; Na+, K(+)-ATPase pump activity and the ground membrane permeability for Na+ and K+ as well as the intra-erythrocyte Na+, K+ and Mg2+ concentrations. Plasma cholesterol, triglycerides, phospholipids, free fatty acids, low- and high-density lipoprotein cholesterol levels and the erythrocyte membrane contents of cholesterol, phospholipids and free fatty acids were obtained from fasting subjects. RESULTS: In single regression analysis the erythrocyte Na(+)-Li+ countertransport and Na+, K+ cotransport activities were negatively related to the erythrocyte membrane cholesterol, phospholipids and free fatty acids contents. The Na+, K(+)-ATPase pump activity as assessed by the ouabain-sensitive Na+ efflux was also inversely related to the membrane cholesterol and phospholipids contents. In multiple regression analysis the red blood cell Na(+)-Li+ countertransport activity was independently and negatively related to the membrane cholesterol and free fatty acids contents. CONCLUSION: Our data show that an elevated level of erythrocyte membrane lipids in normal men is accompanied by lower Na(+)-Li+ countertransport, Na+, K+ cotransport and Na+, K(+)-ATPase pump activities.     

Is there increased cardiovascular risk in essential hypertensive patients with abnormal kinetics of red blood cell sodium-lithium countertransport?

Na+ transport kinetics were studied in red blood cells (RBCs) from 50 essential hypertensive patients and 30 normotensive controls. Seven hypertensive patients were characterized by the following: (1) a maximal rate of Na+-Li+ countertransport higher than an upper normal limit of 525 mumol.litre cells-1.h-1; (2) an apparent dissociation constant for internal Na+ higher than an upper normal limit of 20.4 mmol.litre cells (in only five of the seven hypertensives); (3) no other kinetic abnormality in Na+,K+ pump, Na+,K+ cotransport or passive Na+ permeability. Clinically, hypertensives with abnormal countertransport were characterized by high serum low-density lipoprotein (LDL) cholesterol levels and the presence of electrocardiographic left ventricular hypertrophy (LVH). Conversely, mean values of these two clinical parameters were normal in the remaining hypertensive patients, independently of the presence of other abnormalities in Na+,K+ pump, Na+,K+ cotransport or passive Na+ permeability. In conclusion, the presence of abnormal Na+-Li+ countertransport kinetics in erythrocytes may be associated with an enhanced cardiovascular risk in hypertension.     

The Erythrocyte Sodium - Potassium Cotransport in Hypertensive Patients: Advantages and Limitations

The Na-K cotransport activity was measured in erythrocytes of 123 normotensive and 92 hypertensive patients, using the methodology described by Dagher and Garay. Large overlap of the values obtained in the two populations is observed, in such a way this laboratory test cannot be applied for the discrimination between primary and secondary hypertension.

Moreover, the abnormalities described for the Na-K cotransport do not appear specific for primary hypertension. In this study, the influence of hypertensive heredity, but also obesity on this cotransport system could not be demonstrated. However, this transport activity is significantly decreased in patients with chronic renal failure, during treatment with oestro-progestatives or during the oestrogenic phase of the menstrual cycle.

These data strongly suggest that the cotransport activity could be modified not only by the hypertensive familial predisposition but also by environmental and hormonal influences.     

Blood pressure and erythrocyte Na+ transport systems in a French urban male population

This paper reports an investigation of blood pressure (taken as a continuous variable) as a function of: erythrocyte Na+ content; Na+,K+ pump; Na+,K+ cotransport and Na+,Li+ countertransport fluxes, and passive cation permeabilities in fresh erythrocytes from 129 French males who were living in an urban area and were not under treatment for any medical condition (after allowing for the effects of age, body mass index, alcohol and tobacco consumption). In contrast with previous findings in a North American population, we were unable to confirm that blood pressure was correlated with erythrocyte Na+ content and Na+,K+-AT-Pase activity. Conversely, the only transport parameter correlated (negatively) with blood pressure was outward Na+,K+ cotransport [r = -0.20, P less than 0.05 and r = -0.19, P less than 0.05, for systolic (SAP) and diastolic arterial pressure (DAP), respectively; n = 114]. When allowing for age, body mass index and alcohol consumption, the correlation coefficient between the Na+,K+ cotransport system and blood pressure increased from -0.20 to -0.28 (P less than 0.01) for SAP and from -0.19 to -0.28 (P less than 0.01) for DAP (n = 105). We conclude that the correlations between blood pressure and erythrocyte Na+ transport function could differ between North American and French (or Mediterranean) populations. In any case, a decreased pump or outward Na+,K+ cotransport activity may lead hypertensive subjects to a similar increase in cell Na+ (and Ca2+) content in the vascular wall.     

Sodium and potassium ion transport accelerations in erythrocytes of DOC, DOC-salt, two-kidney, one clip, and spontaneously hypertensive rats. Role of hypokalemia and cell volume

Sodium (Na+) and potassium (K+) transport by the furosemide-sensitive Na+-K+ transport system, the Na+-K+ pump, and the cation leak(s) were studied in erythrocytes from DOC-water, DOC-salt, two-kidney, one clip (Sprague-Dawley), and spontaneously hypertensive rats (Wistar-Kyoto). Rubidium (Rb+) was used as a tracer for K+. After 4 weeks of DOC-salt hypertension, inward K+ (Rb+) transport by the furosemide-sensitive system was increased threefold, and the inward Na+ leak and the red cell Na+ content were elevated by about 50%. The rise in cell Na+ accelerated K+ inward and Na+ outward transport by the Na+-K4 pump, DOC-water hypertension caused similar but less pronounced changes. In two-kidney, one clip hypertension, the Na+ leak and the Na+-K+ pump rates were slightly elevated, and furosemide-sensitive Rb+ uptake tended to be increased. In spontaneously hypertensive rats, furosemide-sensitive Rb+ uptake was accelerated by 50%. The marked hypokalemia in DOC-water and DOC-salt hypertension was associated with a slight loss of red cell K+ and an increase in mean cellular hemoglobin content (MCHC), indicative of cell shrinkage. Hypokalemia induced by dietary K+ deficiency caused alterations in red cell cation transport, content, and cell volume which were qualitatively similar but more pronounced than those seen in DOC-salt hypertension. Osmotic shrinkage in vitro induced a severalfold acceleration of furosemide-sensitive Rb+ uptake, similar to that observed in rat erythrocytes shrunken in vivo in K+-deficient states. It is concluded that the acceleration of furosemide-sensitive K+ (Rb+) transport in erythrocytes of mineralocorticoid hypertensive rats is largely caused by the hypokalemia and consecutive red cell K+ loss and shrinkage, respectively. Mean cellular hemoglobin content (MCHC) is thus a parameter that must be considered in studies on Na+ and K+ transport across the membrane of rat erythrocytes.     

Univalent cation transport in human and rat erythrocytes: its regulation by protein kinase activators and compression

The effect of the activators of protein kinase A (dibutyryl-cAMP) and protein kinase C (beta-phorbolic ether), as well as cell compression, on the rate of 22Na and 86Rb, a radioactive potassium analogue, incorporation by human and rat erythrocytes was investigated. Protein kinase A and protein kinase C activation was accompanied by the activation of Na+, K+-ATP-ase in human and rat erythrocytes as well as increased Na+, K+ cotransport rate in rat erythrocytes. Human erythrocytes responded to protein kinase C activation by a 2 or 3-fold increase in Na+/Na+-antitransport rate, and both human and rat erythrocytes exhibited a manifold increase in the Na+/H+ metabolism rate. Cell compression depressed Na+, K+-ATP-ase activity and increased the rates of Na+/H+ metabolism and the frusemide-inhibited component of potassium transport, the latter two effects being particularly obvious in rat erythrocytes. It is suggested that protein kinase C activation and/or erythrocyte compression may be a direct cause of increased plasmatic membrane permeability for univalent cations in primary hypertension.     

The clinical significance of K-Cl cotransport activity in red cells of patients with HbSC disease

HbSC disease is the second commonest form of sickle cell disease, with poorly understood pathophysiology and few treatments. We studied the role of K-Cl cotransport activity in determining clinical and laboratory features, and investigated its potential role as a biomarker. Samples were collected from 110 patients with HbSC disease and 41 with sickle cell anemia (HbSS). K-Cl cotransport activity was measured in the oxygenated (K-Cl cotransport₁₀₀) and deoxygenated (K-Cl cotransport₀) states, using radioactive tracer studies. K-Cl cotransport activity was high in HbSC and decreased significantly on deoxygenation. K-Cl cotransport activity correlated significantly and positively with the formation of sickle cells. On multiple regression analysis, K-Cl cotransport increased significantly and independently with increasing reticulocyte count and age. K-Cl cotransport activity was increased in patients who attended hospital with acute pain in 2011 compared to those who did not (K-Cl cotransport₁₀₀: mean 3.87 versus 3.20, P=0.009, independent samples T-test; K-Cl cotransport₀: mean 0.96 versus 0.68, P=0.037). On logistic regression only K-Cl cotransport was associated with hospital attendance. Increased K-Cl cotransport activity was associated with the presence of retinopathy, but this effect was confounded by age. This study links variability in a fundamental aspect of cellular pathology with a clinical outcome, suggesting that K-Cl cotransport is central to the pathology of HbSC disease. Increased K-Cl cotransport activity is associated with increasing age, which may be of pathophysiological significance. Effective inhibition of K-Cl cotransport activity is likely to be of therapeutic benefit.     

A Japanese family with hereditary HbH disease--a case report and its gene analysis

Hereditary HbH disease was found in a Japanese family. The propositus showed hypochromic microcytic anemia and chronic hemolysis. HbH inclusion bodies were detected in red cells, and an abnormal band corresponding HbH was found in an isoelectric focusing of the hemolysate. Gene analysis of the propositus revealed double heterozygosity for alpha + and alpha zero thalassemias. Four of six his siblings shared the alpha zero thalassemia and one the alpha + thalassemia. Another one was normal. The alpha + thalassemia was of 3.7 kb-deletion type and alpha zero was close to Southeast Asian type. This is the fourth Japanese family with hereditary HbH disease.