TY - JOUR
T1 - An evaluation of the metabolite indicator method for determining the cytosolic phosphate potential in rat liver cells
AU - Groen, A. K.
AU - Vervoorn, R. C.
AU - Wanders, R. J.
AU - van der Meer, R.
AU - Tager, J. M.
PY - 1982
Y1 - 1982
N2 - The cytosolic phosphate potential was estimated in isolated rat liver parenchymal cells incubated with various gluconeogenic substrates. The value of the cytosolic [ATP]/[ADP][Pi] ratio was either estimated directly from measurements of ATP, ADP and Pi after digitonin fractionation of the cells, or calculated by the metabolite indicator method. When cells were incubated with lactate, pyruvate or alanine so that net flux through the indicator enzymes was in gluconeogenic direction, there was excellent agreement between the values obtained by the two methods over a wide range of fluxes. However, when the cells were incubated with substrates that could be converted both to glucose and to lactate so that net flux through the indicator enzymes was in the glycolytic direction, a large difference in the values of the cytosolic [ATP]/([ATP][Pi]) ratio as derived by the two methods was observed. It is concluded that the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase plus 3-phosphoglycerate kinase is out of equilibrium when flux through the reaction is the glycolytic direction, and that use of the metabolite indicator method for the calculation of the cytosolic phosphate potential under these conditions leads to erroneous values
AB - The cytosolic phosphate potential was estimated in isolated rat liver parenchymal cells incubated with various gluconeogenic substrates. The value of the cytosolic [ATP]/[ADP][Pi] ratio was either estimated directly from measurements of ATP, ADP and Pi after digitonin fractionation of the cells, or calculated by the metabolite indicator method. When cells were incubated with lactate, pyruvate or alanine so that net flux through the indicator enzymes was in gluconeogenic direction, there was excellent agreement between the values obtained by the two methods over a wide range of fluxes. However, when the cells were incubated with substrates that could be converted both to glucose and to lactate so that net flux through the indicator enzymes was in the glycolytic direction, a large difference in the values of the cytosolic [ATP]/([ATP][Pi]) ratio as derived by the two methods was observed. It is concluded that the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase plus 3-phosphoglycerate kinase is out of equilibrium when flux through the reaction is the glycolytic direction, and that use of the metabolite indicator method for the calculation of the cytosolic phosphate potential under these conditions leads to erroneous values
U2 - https://doi.org/10.1016/0167-4889(82)90065-9
DO - https://doi.org/10.1016/0167-4889(82)90065-9
M3 - Article
C2 - 7138915
SN - 0167-4889
VL - 721
SP - 172
EP - 177
JO - BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH
JF - BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH
IS - 2
ER -