Wiesner 1988 Biochim Biophys Acta
| Wiesner RJ, Kreutzer U, Rösen P, Grieshaber MK (1988) Subcellular distribution of malate-aspartate cycle intermediates during normoxia and anoxia in the heart. Biochim Biophys Acta 936:114-23. |
Wiesner RJ, Kreutzer U, Roesen P, Grieshaber MK (1988) Biochim Biophys Acta
Abstract: The subcellular distribution of adenine nucleotides, phosphocreatine and intermediates of the malate-aspartate cycle was investigated in adult rat heart myocytes under normoxia and anoxia. Cytosolic and mitochondrial concentrations of metabolites were determined by a fractionation method using digitonin. Under normoxia, cytosolic/mitochondrial gradients were found for ATP (c/m = 4), AMP (c/m less than 0.01), citrate (c/m = 0.5), aspartate (c/m = 3), glutamate (c/m = 2), while phosphocreatine and glutamine were confined to the cytosolic space. No gradients were found for malate and 2-oxoglutarate. The results show that the transport of electrons from the cytosol into the mitochondria is supported by the glutamate gradient and by a high glutamate/aspartate ratio inside the mitochondria (Glu/Asp = 15) which is maintained by the energy-dependent Glu-Asp exchange across the mitochondrial membrane. Under anoxia, cytosolic glutamate is transaminated with pyruvate, yielding alanine and 2-oxoglutarate, which is oxidized to succinate inside the mitochondria and leaves the cell. The data indicate that stimulation of transamination is caused by a mass action effect following a decrease in cytosolic 2-oxoglutarate which may be due to succinate-2-oxoglutarate exchange across the mitochondrial membrane. Inhibition of the energy-dependent inward transport of glutamate may support this process. • Keywords: Energy metabolism, Malate aspartate cycle, Myocardium, Compartmentation, Anoxia, Isolated myocytes • Bioblast editor: Plangger M
Labels:
Organism: Rat
Tissue;cell: Heart
Enzyme: Inner mt-membrane transporter Regulation: Ion;substrate transport, Amino acid
2018-09
