title: Dependence of gluconeogenesis, urea synthesis, and energy metabolism of hepatocytes on intracellular pH.
abstract: The relationship of intracellular pH to extracellular pH has been measured in suspensions of isolated hepatocytes at 25 degrees C. The internal pH was found to be a linear function of external pH and it changed by 0.45 pH unit per 1.0 unit change in external pH. The internal [H+] was equal to the external [H+] at approximately pH 7.1. Gluconeogenesis, urea synthesis, and oxidative phosphorylation showed different dependencies on the intracellular pH. Gluconeogenesis was the most sensitive to changes in [H+] and it declined by 80% when the intracellular pH decreased from 7.1 to 6.9. Urea synthesis was less pH-dependent, decreasing by about 30% for the same change in the intracellular [H+] whereas respiratory rate showed very little dependence on pH at this temperature. Intracellular [ATP]/[ADP] decreased linearly from 8.5 to 1.5 as the intracellular pH increased from 6.8 to 7.6, while intracellular [Pi] was essentially constant at 3.2 nmol/mg of cells, wet weight. Cytochrome c became more reduced with increasing intracellular pH, from less than 10% at pH 6.8 to 35% at pH 7.7. The calculated free energy of hydrolysis of ATP was nearly independent of pH as was the free energy of electron transfer from the intramitochondrial NAD couple (calculated from the [acetoacetate]/[3-OH-butyrate] ratio) to cytochrome c.
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000502:physiology*; D003574:Cytochrome c Group / Q000378:metabolism; D004734:Energy Metabolism; D005943:Gluconeogenesis; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000502:physiology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D010085:Oxidative Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains; D014508:Urea / Q000096:biosynthesis*
chemical_list: D003574:Cytochrome c Group; D014508:Urea