| 1. |
- Lundberg, Peter, et al.
(författare)
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Fructose 3-phosphate and 5-phosphoribosyl-1-pyrophosphate formation in perfused human erythrocytes : 31P NMR studies
- 1994
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Ingår i: Magnetic Resonance in Medicine. - : John Wiley & Sons. - 0740-3194 .- 1522-2594. ; 31:2, s. 110-121
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Tidskriftsartikel (refereegranskat)abstract
- 31P NMR was used to study the formation of fructose 3-phos-phate (F3P) and 5-phosphoribosyl-1-pyrophosphate (PRPP) in perfused human erythrocytes, in the presence of 10 different combinations and concentrations of glucose, inosine, pyru-vate, fructose, and inorganic phosphate (Pi). (1) The cells were immobilized in alginate-coated agarose threads and perfused with a medium containing fructose, and the level of F3P increased continuously over more than 10 h. The net rate of F3P formation was independent of the concentration of 2,3-bis-phosphoglycerate (2,3-DPG) present in the cells. (2) PRPP was formed in high concentrations, relative to normal, in immobilized cells when they were perfused with a medium containing Pi at a low pH (6.6). (3) The 2,3-DPG level decreased simultaneously when the sample was perfused with a medium containing fructose, but without inosine or pyruvate. The measured intracellular pH and free Mg2+ concentration were constant in these experiments. (4) The experiments confirmed the presence of fructose-3-phosphokinase (E.C. 2.7.1.-) and ribose-phosphate pyrophosphokinase (E.C. 2.7.6.1) activity in the human erythrocytes and that the biosynthetic pathways are active in immobilized cells at 37°C. (5) The rates of accumulation of 2,3-DPG and phosphomonoesters (PME) appeared to be strongly correlated.
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| 2. |
- Lundberg, Peter, et al.
(författare)
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NMR studies of erythrocytes immobilized in agarose and alginate gels
- 1992
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Ingår i: Magnetic Resonance in Medicine. - : John Wiley & Sons. - 0740-3194 .- 1522-2594. ; 25:2, s. 273-288
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Tidskriftsartikel (refereegranskat)abstract
- 31P and 13C NMR were used to study the energy metabolism in perfused, human erythrocytes. The erythrocytes were immobilized in agarose threads, Ca- or Ba-alginate beads, and Ba-alginate-coated agarose threads. Erythrocytes were easily washed out from the agarose threads, but not from alginate-containing gels. Various small molecules, such as hypophosphite, dimethyl methylphosphonate, and methylphosphonate, were taken up from the perfusion medium in a normal manner. In addition, the 2,3-bisphosphoglycerate (2,3-DPG) chemical shifts were sensitive to the oxygen partial pressure suggesting that O2 molecules were diffusing through the gel and modifying the binding of 2,3-DPG to hemoglobin. A combination of inosine and pyruvate stimulated the synthesis of 2,3-DPG, but only if inorganic phosphate was present in the perfusion medium. Inosine only resulted in a dramatic rise in the intracellular sugarphosphate concentrations. Furthermore, [2-13C]glucose was converted to [2-13C]lactate by immobilized cells at a rate which was comparable to that in a control suspension. In summary, immobilization in Ba-alginate-coated agarose threads was an efficient way of trapping human erythrocytes for whole cell NMR investigations.
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