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L Pułaski

Publications and source records attributed to L Pułaski.

9 recordsLinked to original sources
PubMed2000

Transport of organic anions by multidrug resistance-associated protein in the erythrocyte.

The active transport of oxidized glutathione and glutathione S-conjugates has been demonstrated for the first time in erythrocytes and this cell remained the main subject of research on the "glutathione S-conjugate pump" for years. Further studies identifled the "glutathione S-conjugate pump" as multidrug resistance-associated protein (MRP). Even though cells overexpressing MRP and isolated MRP provide useful information on MRP structure and function, the erythrocyte remains an interesting model cell for studies of MRP1 in its natural environment, including the substrate specificity and ATPase activity of the protein.

ATP-Binding Cassette Transporters↗
PubMed1998

Is the glutathione S-conjugate pump a flippase?

A hypothesis of the flippase nature of the glutathione S-conjugate transport is presented. Experimental premises for this hypothesis include interaction of glutathione S-conjugates with the membrane, as demonstrated by their effects on membrane fluidity, quenching of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene fluorescence and induction of echinocytosis by 2,4-dinitrophenyl-S-glutathione (DNP-SG). This hypothesis can rationalize, i. a., observations of the enhancement of DNP-SG transport by butanol and stimulation of erythrocyte membrane Mg(2+)-ATPase activity by albumin-coupled DNP-SG.

1-Butanol↗
PubMed1996

An electron spin resonance assay of glutathione S-conjugate transport.

A method for studying export of glutathione S-conjugates from cells is proposed based on the use of the spin label tempo-maleimide. This compound is conjugated intracellularly with glutathione and the concentration of the exported conjugate is measured in cell supernatants in an electron spin resonance spectrometer after reoxidation with ferricyanide. This method allows for measurements of micromolar concentrations of the conjugate and requires low amounts of cells.

Adult↗
PubMed1995

Transport of bimane-S-glutathione in human erythrocytes.

Export of glutathione S-conjugate of bimane (BSG) was studied in human erythrocytes. Characteristics of the BSG transport is similar to that of dinitrophenyl-S-glutathione (DNP-SG). BSG transport has two kinetic components, one of high affinity and low capacity (Km = 7.4 +/- 0.2 mumol/ml cells, Vm = 2.7 +/- 0.1 nmol/min per ml RBC) and another of low affinity and high capacity (Km = 242 +/- 8 mumol/ml cells, Vm = 9.6 +/- 1.6 nmol/min per ml RBC). BSG export is inhibited by vanadate (Ki = 65 +/- 6 microM) and fluoride (Ki = 11.4 +/- 0.8 mM). Activation energy of the transport is 67 +/- 7 kJ/mol. BSG transport is independent of membrane potential; its rate increases with pH in the pH range of 6-8, in line with the assumption that the anionic conjugate is cotransported with proton. BSG import to erythrocyte membrane inside-out vesicles is stimulated by ATP. Fluorimetric measurements of BSG export require low amounts of cells and may also be useful for other cell types as an alternative to studies of glutatione S-conjugate transport using radioactive substrates.

Biological Transport↗
PubMed1995

Effect of inhibitors on the transport of dinitrophenyl-S-glutathione in human erythrocytes.

Effect of inhibitors on and pH dependence of the export of dinitrophenyl-S-glutathione (DNP-SG), a glutathione S-conjugate formed upon in vivo conjugation of 1-chloro-2,4-dinitrobenzene to glutathione, was studied in intact human erythrocytes. The transport was inhibited by orthovanadate (IC50 = 80 microM) and fluoride (IC50 = 9 nM). Erythrocyte anion exchange (Band 3) protein inhibitors DIDS and SITS did not exert any significant effect on the transport. The transport rate increased with increasing extracellular pH in the range of 6.0-8.0. The Arrhenius activation energy of the process was 72.4 +/- 1.3 kJ/mol. Membrane potential, extracellular sodium/potassium concentration ratio and extracellular osmolality in the range 300-600 mOsm did not influence the export rate.

Biological Transport↗
PubMed1995

Peroxides inhibit the glutathione S-conjugate pump.

Tert-Butyl hydroperoxide (100-300 microM) was found to inhibit the active efflux of dinitrophenyl-S-glutathione (DNP-SG) from human erythrocytes. From among amino acid peroxides generated by irradiation of amino acid (proline, valine and leucine) solutions, valine hydroperoxide (150 microM) had a similar effect on the DNP-SG transport. As the transport of glutathione S-conjugates is an important step of cellular detoxication, these results indicate that oxidative stress may impair cellular resistance to chemical stress of other kinds. t-Butyl and amino acid peroxides upon interaction with hemoglobin and whole erythrocytes produce free radicals which may be responsible for the damage to the glutathione S-conjugate pump of the erythrocyte membrane.

Biological Transport, Active↗
PubMedDate not supplied

Transcriptional upregulation of the human MRP2 gene expression by serine/threonine protein kinase inhibitors.

Transcriptional regulation by cellular signalling pathways of multidrug resistance proteins that pump anticancer drugs out of cells is one of key issues in the development of the multidrug resistance phenotype. In our study, we have used the reporter gene approach as well as determination of mRNA levels in two cancer cell lines of human origin, MCF-7 and A549, to study the regulation of multidrug resistance proteins 2 and 3 (MRP2 AND MRP3) by serine/threonine protein kinases. Since a prototypic PKC inducer, PMA, caused a marked upregulation of transcription from both human MRP2 and MRP3 promoters, a role for PKC isoforms in positive control of expression of these proteins could be postulated. Interestingly, broad-spectrum serine-threonine protein kinase inhibitors which also inhibit PKC, staurosporine and H-7, stimulated expression from the MRP2 promoter instead of inhibiting it. This effect was not seen for MRP3. MRP2 induction by staurosporine and H-7 was shown to have phenotypic consequences in whole cells, rendering them more resistant to etoposide and increasing their ability to export calcein through the plasma membrane. These results point to the involvement of serine/threonine protein kinases in negative regulation of the human MRP2 gene and to the necessity of testing novel anti-cancer drugs acting as protein kinase inhibitors with regard to their potential ability to induce multidrug resistance.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗