Role of chloride in potassium transport through a K-Cl cotransport system in human red blood cells

1989 ◽  
Vol 256 (5) ◽  
pp. C994-C1003 ◽  
Author(s):  
C. Brugnara ◽  
T. Van Ha ◽  
D. C. Tosteson
Keyword(s):  
Membrane Potential ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Normal Subjects ◽  
Similar Data ◽  
Human Red Blood Cells ◽  
Dense Fraction ◽  
Cotransport System ◽  
Low K

In this paper, we report experiments demonstrating the coupling of Cl and K movements in a volume-dependent K-Cl cotransport system in human red blood cells. We show that an outwardly directed Cl gradient can promote net K efflux against an inwardly directed K gradient at constant membrane potential. Red blood cell membrane potential was kept constant by using anions that are not transported through the K-Cl cotransport system but that are more permeable than Cl (NO3 and SCN). Under these conditions, when the activities of band 3 (capnophorin)-mediated anion exchange and of the carbonic anhydrase have been inhibited, it is possible to maintain a Cl gradient at constant membrane potential. Similar data were obtained in human red blood cells (least dense fraction from normal subjects and whole blood from patients with homozygous hemoglobin S disease), in rabbit red blood cells, and in low-K sheep red blood cells. These data confirm that the volume-dependent Cl-dependent K movement in these cells operates through coupled K-Cl cotransport.

Catechol O-Methyltransferase in Red Blood Cells of Schizophrenic, Depressed, and Normal Human Subjects

1976 ◽  
Vol 128 (2) ◽  
pp. 184-187 ◽  
Author(s):  
Helen L. White ◽  
Malcolm N. McLeod ◽  
Jonathan R. T. Davidson
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Human Subjects ◽  
Normal Subjects ◽  
Enzyme Preparations ◽  
Human Red Blood Cells ◽  
Schizophrenic Patients ◽  
Normal Human ◽  
The Mean ◽  
Isoelectric Ph

SummaryCatechol O-methyltransferase of lysed human red blood cells was assayed under optimal conditions, using saturating concentrations of the substrates, S-adenosyl-L-methionine and 3,4-dihydroxybenzoic acid. The mean enzyme activity found in 24 normal subjects was 29.2 nmol/hr/ml RBC. The mean activity in blood of 33 female unipolar depressives was not significantly different from normal. However, higher enzyme activities were observed in the blood of 11 schizophrenic patients (38.9 nmol/hr/ml RBC). Partially purified enzyme preparations from blood of normal and schizophrenic individuals were indistinguishable with respect to substrate specificities, isoelectric pH values, and ratios of the two O-methylated products. Therefore it is unlikely that any defect in O-methylation which may occur in schizophrenia can be attributed to a change in the intrinsic properties of erythrocyte catechol O-methyltransferase.

scholarly journals Detection of acyl-CoA-binding protein in human red blood cells and investigation of its role in membrane phospholipid renewal

1995 ◽  
Vol 306 (3) ◽  
pp. 793-799 ◽  
Author(s):  
H Fyrst ◽  
J Knudsen ◽  
M A Schott ◽  
B H Lubin ◽  
F A Kuypers
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Human Liver ◽  
Plasma Membranes ◽  
Binding Protein ◽  
Human Red Blood Cells ◽  
Low Concentrations ◽  
Membrane Bound ◽  
High Concentrations

Acyl-CoA-binding protein (ACBP) has been identified in a number of tissues and shown to affect the intracellular distribution and utilization of acyl-CoA. We have detected ACBP in the cytosol but not the membrane of human red blood cells and, using an e.l.i.s.a. with antibodies prepared against human liver ACBP, found that its concentration was 0.5 microM. To investigate the role of ACBP in human red blood cells, we added purified human liver ACBP and radiolabelled acyl-CoA to isolated membranes from these cells. ACBP prevented high concentrations of acyl-CoA from binding to the membrane but could not keep the acyl-CoA in the aqueous phase at low concentrations. This suggested the presence of a pool in the membrane with a binding affinity for acyl-CoA that was greater than that of ACBP for acyl-CoA. In the presence of lysophospholipid, this membrane-bound pool of acyl-CoA was rapidly used as a substrate by acyl-CoA:lysophospholipid acyltransferase (LAT) to generate phospholipid from lysophospholipid. We also found that ACBP-bound acyl-CoA was preferred over free acyl-CoA as a substrate by LAT. These results are the first documentation that human red blood cells contain ACBP and that this protein can affect the utilization of acyl-CoA in plasma membranes of these cells. The interactions between acyl-CoA, ACBP and the membrane suggest that there are several pools of acyl-CoA in the human red blood cell and that ACBP may have a role in regulating their distribution and fate.

scholarly journals Investigations on the role of hemoglobin in sulfide metabolism by intact human red blood cells

2018 ◽  
Vol 149 ◽  
pp. 163-173 ◽  
Author(s):  
Christopher L. Bianco ◽  
Anton Savitsky ◽  
Martin Feelisch ◽  
Miriam M. Cortese-Krott
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Human Red Blood Cells

Calcium-induced transient potassium efflux in human red blood cells

1986 ◽  
Vol 250 (1) ◽  
pp. C55-C64 ◽  
Author(s):  
J. S. Adorante ◽  
R. I. Macey
Keyword(s):  
Ionic Strength ◽  
Phase I ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Potassium Efflux ◽  
Pump Failure ◽  
Human Red Blood Cells ◽  
Low Ionic Strength ◽  
Low K ◽  
Phase Phase

Human red blood cells pretreated with low-ionic-strength solutions and resuspended in saline respond biphasically to extracellular Ca. At first, addition of Ca causes a large transient K efflux of as much as 600 mM . liter cell H2O-1 . h-1; this is followed by a decrease in K flux below control levels. The first phase (phase I) resembles the Gardos effect in several respects. It is inhibited by oligomycin, by external K, and by increased exposure time to Ca. Further, the K permeability of phase I is similar to that of the Gardos effect (5 X 10(-8)-9 X 10(-8) cm/s), and the cells hyperpolarize in a low-K medium when Ca2+ is added. However, phase I is not identical to the Gardos phenomenon. For example, La, which prevents the Gardos response, is ineffective on phase I. Moreover, external Ba prevents the development of phase I but not the Gardos response, whereas internal Ba prevents the Gardos response. Attempts to demonstrate a Ca leak or pump failure during phase I have failed; passive Ca movements of both treated and normal cells are similar. The results suggest that low-ionic-strength solution exposes Ca-sensitive sites to the external medium; these sites are maintained when the cells are returned to saline.

Proton-sulfate cotransport: external proton activation of sulfate influx into human red blood cells

1984 ◽  
Vol 247 (3) ◽  
pp. C247-C259 ◽  
Author(s):  
M. A. Milanick ◽  
R. B. Gunn
Keyword(s):  
Membrane Potential ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Half Cycle ◽  
Ph Values ◽  
Human Red Blood Cells ◽  
Internal Ph ◽  
Ph Range ◽  
External Ph ◽  
Chloride Concentrations

Sulfate influx into human red blood cells was measured at 0 and 22 degrees C at several fixed external pH values between 3 and 10. These cells had normal internal pH and chloride concentrations so that sulfate influx was not limited by the efflux half-cycle reactions. The flux was a Michaelis-Menten function of sulfate concentration at each pH with K1/2SO4 = 4-10 mM. External protons activated influx 100-fold at a single site with a pK = 5.9 at 22 degrees C and 5.5 at 0 degrees C. This pK is similar to the value 5.99 +/- 0.3 for external proton binding to the sulfate-loaded transporter at 0 degrees C (J. Gen. Physiol. 79: 87-114, 1982). The flux was stilbene sensitive even in valinomycin-treated cells and was independent of membrane potential. This proton-activated influx appears to be proton-sulfate cotransport. At high pH there was a proton-independent flux that was membrane potential and stilbene sensitive. This proton-insensitive flux appears to be SO4(2-)/Cl- exchange or net sulfate influx. The sulfate influx over the entire pH range may be described in terms of an equation for the sum of the influxes through these two pathways on band 3.

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