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J O Wieth

Publications and source records attributed to J O Wieth.

14 recordsLinked to original sources
PubMed1991

[Congenital stomatocytosis with hemolytic anemia--with abnormal cation permeability and defective membrane proteins].

A case of hereditary stomatocytosis with haemolytic anaemia in a nine year-old girl is presented. This rare syndrome is associated with increased permeability for monovalent cations across the erythrocyte membrane leading to high intracellular sodium (72 mmol/l erythrocytes) and low potassium (32 mmol/l erythrocytes) accompanied by an increased water content. In our patient the passive Na+ and K+ flux were increased to approximately 20 times normal with a compensatory maximal activation of the normal Na, K transport. The cation permeability defect was partly corrected in vitro by a bifunctional imidoester, dimethyl suberimidate. Electrophoresis of solubilizer membrane proteins revealed changes in the protein band pattern with reduction of band 7, as reported previously, and increase in the band 4.1a/4.1b ratio and increased band 4.8.

Anemia, Hemolytic, Congenital↗
PubMed1989

Functional carboxyl groups in the red cell anion exchange protein. Modification with an impermeant carbodiimide.

Anion exchange in human red blood cell membranes was inactivated using the impermeant carbodiimide 1-ethyl-3-(4-azonia-4,4-dimethylpentyl)-carbodiimide (EAC). The inactivation time course was biphasic: at 30 mM EAC, approximately 50% of the exchange capacity was inactivated within approximately 15 min; this was followed by a phase in which irreversible exchange inactivation was approximately 100-fold slower. The rate and extent of inactivation was enhanced in the presence of the nucleophile tyrosine ethyl ester (TEE), suggesting that the inactivation is the result of carboxyl group modification. Inactivation (to a maximum of 10% residual exchange activity) was also enhanced by the reversible inhibitor of anion exchange 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS) at concentrations that were 10(3)-10(4) times higher than those necessary for inhibition of anion exchange. The extracellular binding site for stilbenedisulfonates is essentially intact after carbodiimide modification: the irreversible inhibitor of anion exchange 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) eliminated (most of) the residual exchange activity: DNDS inhibited the residual (DIDS-sensitive) Cl- at concentrations similar to those that inhibit Cl- exchange of unmodified membranes: and Cl- efflux is activated by extracellular Cl-, with half-maximal activation at approximately 3 mM Cl-, which is similar to the value for unmodified membranes. But the residual anion exchange function after maximum inactivation is insensitive to changes of extra- and intracellular pH between pH 5 and 7. The titratable group with a pKa of approximately 5.4, which must be deprotonated for normal function of the native anion exchanger, thus appears to be lost after EAC modification.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

Kinetics of reversible DIDS inhibition of chloride self exchange in human erythrocytes.

The capnophorin (band 3)-mediated chloride self exchange flux in intact erythrocytes and in resealed erythrocyte ghosts was determined at pH 7.3 by measuring the unidirectional efflux of 36Cl-. The time-dependent irreversible inactivation of the anion transport system by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) was measured as the relative change of the unidirectional 36Cl efflux rate. The rate of covalent DIDS binding under conditions of excess DIDS in solution that ensure a complete irreversible inhibition followed an exponential time course with a rate coefficient Kcov (min-1). The Arrhenius activation enthalpy of Kcov was constant, 114 kJ/mol, at 0-38 degrees C. At 38 and 0 degrees C, Kcov was 0.5 min-1 [half time (T1/2) = ln2/Kcov = 1.3 min] and 0.004 min-1 (T1/2 = 178 min), respectively. The slow irreversible DIDS binding to the anion transport system at 0 degrees C allows a determination of the kinetics of the reversible DIDS reaction. The pseudo first-order rate constant for binding, kon, was 3.5 X 10(5) (M.s)-1. The apparent dissociation constant, KD, determined from the steady-state binding to the erythrocyte membrane was 3.1 X 10(-8) M at an equal internal and external Cl- concentration of 165 mM (0 degrees C). The value of KD shows that DIDS is the most efficient reversible inhibitor among the stilbene derivatives so far studied. Maximum reversible inhibition by DIDS was obtained by binding of a minimum of approximately 10(6) molecules/cell membrane. The number is similar to that obtained from studies of irreversible DIDS binding.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1979

Organotin-mediated exchange diffusion of anions in human red cells.

Organotin cations (R3Sn+) form electrically neutral ion pairs with monovalent anions. It is demonstrated that the tin derivatives induce exchange diffusion of chloride in red cells and resealed ghosts, without any detectable increase of membrane permeability to net movements of chloride ions. The obligatory anion exchange is believed to be due to the permeation of electroneural ion pairs, whereas the organic cation (R3Sn+) has an extremely low membrane permeability. Exchange fluxes of chloride increased with the lipophilicity of the substituting group (R3). At the same molar concentration of organotin, the relative potencies of the tin derivatives as anion carriers (with trimethyltin as a reference) were: methyl 1, ethyl 30, propyl = phenyl 1,00, and butyl 10,000. Tributyltin-mediated anion exchange was studied in detail. The organotin-induced anion transport increased through the sequence: F- less than Cl- less than Br- less than I- = SCN- less than OH-. Partitioning of tributyltin into red cell membranes was greater in iodide than in chloride media (partition coefficients 6.6 and 1.7 x 10(-3) cm, respectively). Bicarbonate, fluoride, nitrate, phosphate, and sulphate did not exchange with chloride in the presence of tributyltin. Chloride exchange fluxes increased linearly with tributylin concentrations up to 10(-5) M, and with chloride concentrations up to at least 0.9 M. The apparent turnover number for tributyltin-mediated chloride exchange increased from 15 to 1,350 s-1 between 0 and 38 degrees C. These figures are minimum turnover numbers, because it is not known what fraction of the organotin in the membrane exists as chloride ion pairs.

Adsorption↗
PubMed1979

Tributyltin-mediated exchange diffusion of halides in lipid bilayers.

This paper describes the effect of tributyltin (TBT) on the inorganic anion permeability of lipid bilayers. When this compound is added in micromolar concentrations to one or both sides of a phosphatidyl ethanolamine (PE) membrane formed in 0.1 M NaCl or KCl (pH 7), there is no change in the electrical conductance. Under these circumstances, the Cl self-exchange flux measured with 36Cl (MCl) increases from a value of approximately 10(-12) mol.cm-2.s-1, to approximately 10(-8) mol.cm-2.s-1. It was further found that the relation between chloride flux and [TBT] and [Cl] can be described as: MCl = B[TBT] [Cl]. When chloride was replaced by an equimolar concentration of different univalent anions in the trans compartment, the heteroexchange flux of chloride followed the sequence: I greater than Br greater than Cl greater than F greater than NO3. Under all experimental conditions tested, the chloride flux was always more than 10(3) times the maximum flux predicted from the value of the membrane conductance, and at least 100 times higher than the expected fluxes of ion pairs (TBT-Cl) diffusing across the unstirred layers. Thus, the mechanism by which tributyltin increases anion permeability in bilayers seems to be that of an obligatory exchange diffusion, with the reaction between tributyltin and the halides occurring at the membrane surface. Measurements of interfacial potentials indicate that tributyltin chloride lowers the positive intrinsic dipole potential of PE membranes by approximately 70 mV (at a TBT concentration of 30 microM) without substantial alteration of other parameters of the bilayer. The estimated adsorption coefficient of TBT-Cl was found to be 3 x 10(-4) cm.

Bromides↗
PubMed1979

Bicarbonate exchange through the human red cell membrane determined with [14C] bicarbonate.

1. Bicarbonate transport across human red cell membranes was studied between 0 and 10 degrees C at alkaline pH values by determining the efflux of 14C-labelled bicarbonate from resealed erythrocyte ghosts. Transfer of labelled CO2 was eliminated as a source of error, when formation of intracellular 14CO2 was inhibited with carbonic anhydrase inhibitors. The study showed that there are no fundamental differences between the characteristics of bicarbonate and of chloride self-exchange as has been inferred from previous studies of chloride-bicarbonate exchange. 2. Efflux of radioactivity could be reduced more than 99% by reversible and irreversible inhibitors of anion transport. Inhibition of both chloride and bicarbonate self-exchange was linearly related to the binding of 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) to the membranes. Complete (i.e. greater than 99%) inhibition was obtained after binding of 1.2 x 10(6) DIDS molecules per cell. 3. Bicarbonate self-exchange proved a saturable function of bicarbonate concentration, with a maximum at external and internal concentrations of approximately 100 mM, showing self-depression at higher bicarbonate concentrations, and half-maximum exchange flux at a concentration of 10 mM. The results were consistent with the hypothesis that the exchange mechanism has two anion binding sites, one mediating ion transport and the other causing transport inhibition. 4. Maximum exchange flux of bicarbonate was about 30% larger thant that of chloride, and the affinity of bicarbonate for the transport site was about three times larger than that of chloride. The apparent activation energy of bicarbonate exchange was 28 kcal/mole, the same order of magnitude as found for other inorganic anions between 0 and 10 degrees C. 5. The ability of other inorganic anions to exchange with bicarbonate decreased in the sequence Cl greater than NO3 greater than F greater than Br greater than or equal to I, corresponding to the sequence of the rate of self-exchange of halides. 6. Counter-transport of bicarbonate could be driven by a chloride gradient, when ghosts containing KCl were suspended in a medium containing traces of labelled bicarbonate in addition to a non-permeating anion. Concentration ratios (ci/co) up to about 1000 could be obtained. 7. It is concluded that bicarbonate is transported by the inorganic anion exchange mechanism of the erythrocyte membrane. The slight differences between the exchange kinetics of chloride and bicarbonate were explained by differing affinities of the two anions for the two anion binding sites of the transport system.

Bicarbonates↗
PubMed1978

[Biophysics].

Explore the source record for details and available documents.

Bicarbonates↗
PubMed1978

Effects of bicarbonate on lithium transport in human red cells.

Lithium influx into human erythrocytes increased 12-fold, when chloride was replaced with bicarbonate in a 150 mM lithium medium (38 degrees C. pH 7.4). The increase was linearly related to both lithium- and bicarbonate concentration, and was completely eliminated by the amino reagent 4, 4'- diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). DIDS binds to an integral membrane protein (mol wt approximately 10(5) dalton) involved in anion exchange. Inhibition of both anion exchange and of bicarbonate-stimulated lithium influx was linearly related to DIDS binding. 1.1 X 10(6) DIDS molecules per cell caused complete inhibition of both processes. Both Cl- and Li+ can apparently be transported by the anion transport mechanism. The results support our previous proposal that bicarbonate-induced lithium permeability is due to transport of lithium-carbonate ion pairs (LiCO-3). DIDS-sensitive lithium influx had a high activation energy (24 kcal/mol), compatible with transport by the anion exchange mechanism. We have examined how variations of passive lithium permeability, induced by bicarbonate, affect the sodium-driven lithium counter-transport in human erythrocytes. The ability of the counter-transport system to establish a lithium gradient across the membrane decrease linearly with bicarbonate concentration in the medium. The counter-transport system was unaffected by DIDS treatement. At a plasma bicarbonate concentration of 24 mM, two-thirds of the lithium influx is mediated by the bicarbonate-stimulated pathway, and the fraction will increase significantly in metabolic alkalosis.

Bicarbonates↗
PubMed1977

Separative pathways for urea and water, and for chloride in chicken erythrocytes.

1. Urea and water permeabilities of chicken erythrocytes are considerably lower than those of mammalian red cells. 2. The permeabilities to urea, thiourea and to N-methylurea (about 10(-6) cm/sec at 25 degrees C) were independent of concentration within a very broad range, and we found no evidence of interaction between transport of analogue molecules. The activation energies were between 17 and 19 kcal/mole, and urea transport was not inhibited by phloretin, which inhibits urea transport in mammalian red cells. 3. The water permeability of chicken red cells (as measured by the diffusion of tritiated water) was 1-35 X 10(-3) cm/sec at 25 degrees C. The activation energy was 10 kcal/mole, and the water permeability was not affected by phloretin or parachloromercuribenzoate. 4. It is concluded that the urea and water permeabilities of the chicken erythrocyte membrane are similar to those of a non-porous bimolecular phospholipid membrane. 5. Like the red cells of other animal species the chicken red cell membrane contains an anion transport system, mediating a rapid exchange of chloride across the cell membranes. The pH dependence, temperature dependence, and sensitivity to inhibitors were similar to the properties of the anion transport system found in mammalian red cells. Our study shows, therefore, that the transport system offers a highly specific pathway to the exchange of anions, without presenting an inspecific leak to the permeation of water and urea.

Animals↗
PubMed1976

Glycerol transport in human red cells.

The kinetics of 14C-glycerol exchange was studied in human red cells. Glycerol appeared to be transported by two mechanisms: (i) by facilitated diffusion with permeability depending on glycerol concentration, and (ii) by an unspecific pathway, presumably representing the diffusion of individual glycerol molecules through the membrane with permeability independent of glycerol concentration. The latter permeability was 8 X 10(-8) cm/s at 20 degrees C, it was independent of pH, and had an activation energy of 25 kcal/mol. The facilitated transport of glycerol was completely inhibited by Cu++, and the activation energy was low, about 10 kcal/mol. The transport system was competitively inhibited by H+, reacting with at least three hydrogen analogue, as well as dimethylsulfoxide (a hydrogen bonding molecule with no structural resemblance to glycerol), inhibited glycerol transport competitively. Steins "dimerizer hypothesis" was revised according to our findings. A kinetic scheme describing the reactions of a transport controlling site with glycerol is presented in the Appendix. It is demonstrated in the article that the scheme accounts for out experimental results.

Biological Transport↗
PubMed1976

Chloride transport in human erythrocytes and ghosts: a quantitative comparison.

1. Homogeneous preparations of resealed ghosts with intracellular KCl concentrations between 15 and 900 mM could be prepared. Virtually all ghosts sealed to chloride. The chloride transport system was found not to be damaged: a quantitative comparison of the self-exchange of 36Cl- across intact and resealed membranes showed that both the transport capacity and a number of characteristic properties were identical (saturation kinetics, temperature dependence and the effect of inhibitors). 2. Due to the absence of intracellular titratable buffers intracellular chloride concentration in ghosts vary only slightly between pH5 and 11. The unidirectional exchange flux was constant between pH 7 and 11, showing that the transport system does not have a functionally important titratable group in the alkaline range, as previously assumed. The decrease of transport below pH 7 is similar in intact erythrocytes and ghosts. 3. Mean cellular volume of the resealed ghosts was a function of the amount of KCl added at 'reversal', before the ghosts are sealed. The ghosts shrank by osmosis when KCl was added to the suspension of 'unsealed' ghosts. The reflexion coefficient of sucrose (and therefore the osmotic effect) is larger than that of KCl. It was, therefore, possible to demonstrate that volume changes do not affect the chloride transport across the human red cell membrane. Unidirectional chloride fluxes at a KCl concentration of 165 mM were independent of ghost volume (100-40 mum3).

Biological Transport↗
PubMed1975

Some effects of low pH on chloride exchange in human red blood cells.

In order to test the range of pH values over which the titratable carried model for inorganic anion exchange is valid, chloride self-exchange across human red blood cells was examined between pH 4.75 and 5.7 at 0 decrees c. It was found that chloride self-exchange flux had a minimum near pH 5 and increased again with further increase in hydrogen ion activity. The Arrhenius activation energy for chloride exchange was greatly reduced at low pH values. The chloride flux at pH 5.1 did not show the saturation kinetics reported at higher pH values but was proportional to the value of the chloride concentration squared. In addition, the extent of inhibition of chloride self-exchange flux by phloretin was reduced at low pH. Our interpretation of these findings is that the carrier-mediated flux becomes a progressively smaller fraction of the total flux at lower pH values and that a different transport mode requiring two chloride ions to form the permeant species and having a low specificity and temperature dependence becomes significant below pH5. A possible mechanism for this transport is that chloride crosses red cell membranes as dimers of HCl at these very low pH values.

Biological Transport↗