The connection between ionophore-mediated Ca2+-movements and intermediary metabolism in human red cells. II. Site and mode of glycolytic activation during Ca2+-loading |
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Authors: | P. Arese A. Bosia G.P. Pescarmona U. Till |
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Affiliation: | 1. Istituto di Chimica Biologica, Università di Sassari, 07100 Sassari, Italy;2. Physiologisch-chemisches Institut, Friedrich-Schiller-Universität, Jena, DDR. |
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Abstract: | Human red cells (RBC) respond to moderate Ca2+-loading with increased ATP consumption and stimulation of glycolytic flux. 1. Ca2+-induced metabolite transitions at different pH-values showed a clearcut crossover at the glyceraldehyde-3-phosphate dehydrogenase/3-phosphoglycerate kinase (. 2. The behavior of glycolytic metabolites in iodoacetate-treated, GAPDH-inhibited, and in phosphoenolpyruvate-loaded RBC ruled out activation of hexokinase, phosphofructokinase and pyruvate kinase. 3. Glycolytic stimulation is linked to Ca2+-extrusion rate and not to the loaded Ca2+. 4. Adenine nucleotides and inorganic phosphate could be ruled out as the connecting link between glycolytic activation and Ca2+-extrusion. 5. NADH oxidation was observed at all pH-values studied when the RBC were incubated either at low or high extracellular potassium. NADH is product-inhibitor of GAPDH. The concentration (34 μM) of thermodynamically free NADH calculated from the equilibrium reactants was in the inhibitory range: any decrease in NADH is therefore followed by activation of GAPDH. ratio seems to be the connecting link between ATP consuming ion transport and ATP generation by glycolysis. |
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Keywords: | Reprint requests to P.A. |
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