The transport of Pi between the cytosol and the mitochondria was investigated in perfused rat liver stimulated with phenylephrine and metabolic precursors of glucose and urea: pyruvate, lactate, NH4+ and ornithine. The relative concentrations of phosphorus metabolites in the liver were measured by 31P-n.m.r. spectroscopy. When added simultaneously, phenylephrine and the precursors induced a decrease in the Pi level which in 4-5 min reached a new steady state at 73% of the control level. After 5 min or more of stimulation the ATP level had also decreased. When the stimulation ended, Pi and ATP returned to their initial levels within 15 min. In mitochondria isolated after 5 min of stimulation, Pi was increased more than 2-fold as compared with control mitochondria and, in addition, an accumulation of Pi from the perfusion buffer into the liver was observed. Phenylephrine by itself did not cause any significant changes in the ATP or Pi levels, whereas the glucose and urea precursors in the absence of phenylephrine induced a 9% decrease in Pi, while ATP remained constant. The Pi content of mitochondria isolated under these conditions was not significantly increased as compared with control mitochondria. These results showed that Pi accumulated into the mitochondria by a mechanism possibly involving exchange for malate, and that a major part of the intramitochondrial Pi was invisible by n.m.r.
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February 1994
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Research Article|
February 15 1994
Effect of phenylephrine on the compartmentation of inorganic phosphate in perfused rat liver during gluconeogenesis and urea synthesis: a 31P-n.m.r.-spectroscopic study
O Eriksson;
O Eriksson
*Helsinki Bioenergetics Group, Department of Medical Chemistry, University of Helsinki, P.O. Box 8, SF-00014 Helsingin Yliopisto, Finland.
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P Pollesello;
P Pollesello
†Department of Biochemistry and Biophysics and Chemistry of Macromolecules, University of Trieste, Via L. Girogeri 1, 1-34127 Trieste, Italy.
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N E L Saris
N E L Saris
*Helsinki Bioenergetics Group, Department of Medical Chemistry, University of Helsinki, P.O. Box 8, SF-00014 Helsingin Yliopisto, Finland.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1994 The Biochemical Society, London
1994
Biochem J (1994) 298 (1): 17–21.
Citation
O Eriksson, P Pollesello, N E L Saris; Effect of phenylephrine on the compartmentation of inorganic phosphate in perfused rat liver during gluconeogenesis and urea synthesis: a 31P-n.m.r.-spectroscopic study. Biochem J 15 February 1994; 298 (1): 17–21. doi: https://doi.org/10.1042/bj2980017
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