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Oxygen and substrate dependence of hepatic cellular respiration: Sinusoidal oxygen gradient and effects of ethanol in isolated perfused liver and hepatocytes
Author(s) -
Kekonen Eija M.,
Jauhonen V. Pekka,
Hassinen Ilmo E.
Publication year - 1987
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041330115
Subject(s) - oxygen , respiration , ethanol , oxidative phosphorylation , cellular respiration , hepatocyte , chemistry , cytochrome , biophysics , metabolism , hemoglobin , nad+ kinase , biochemistry , mitochondrion , biology , anatomy , enzyme , organic chemistry , in vitro
The oxygen dependence of hepatic cellular respiration was studied by employing simultaneous organ spectrophotometry of cytochromes and hemoglobin, the latter used as an intrasinusoidal optical oxygen probe. The K m of cytochrome aa 3 for oxygen was found to be 6.8 μM in the isolated perfused liver and 0.3 μM in suspensions of isolated hepatocytes. The results indicate that the sinusolid‐to‐cell pO 2 gradient is about 5 torr. Optical determination of the average effective pO 2 indicates that the axial sinusoidal O 2 profile does not conform to zero‐order O 2 uptake in the liver. Because of extensive NAD + reduction, ethanol increases the thermodynamic driving force of oxidative phosphorylation, and it also increased the oxygen consumption in both the perfused liver and the hepatocyte suspension, but had no effect on the grade of steady‐state cytochrome aa 3 reduction, the cellular energy state [ATP]/[ADP]·[P i ], or the K m of cytochrome aa 3 for oxygen. The results indicate that hepatic energy metabolism is oxygen independent at very low O 2 concentrations, but that the sinusoidal axial O 2 concentration is anomalous, probably due to the spatial arrangement of the metabolizing systems.