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Gluconeogenesis from Dihydroxyacetone in Rat Hepatocytes during the Shift from a Low Protein, High Carbohydrate to a High Protein, Carbohydrate-Free Diet^1,2,

Centre de Recherches sur la Nutrition du CNRS, 9 rue Jules Hetzel, 92190 Meudon-Bellevue, France

Pyruvate kinase activity and rates of gluconeogenesis and glycolysis in rat hepatocytes were evaluated by production of glucose and lactate + pyruvate from dihydroxyacetone during the first 48 hours after the shift from a low protein, high carbohydrate diet to a high protein, carbohydrate-free diet. The effect of glucagon was also studied. In the absence of glucagon, 11–17 hours after the dietary shift when glycogen was lowest, gluconeogenesis was maximal and glycolysis minimal. The concentration of fructose 1,6-bisphosphate was high and did not change during the experiment. The activity ratio of pyruvate kinase measured with phosphoenolpyruvate (PEP) (v_0.5 mM PEP/V₄mM PEP) was high in crude extracts and low in (NH₄)₂SO₄-treated extracts, but remained unchanged during the whole experiment. There was no correlation of the rates of gluconeogenesis or glycolysis from dihydroxyacetone with the activity ratio of pyruvate kinase. With glucagon, gluconeogenesis from dihydroxyacetone was increased and a concurrent decrease in glycolysis was paralleled with a decrease in the fructose 1,6-bisphosphate concentration and in the activity ratio of pyruvate kinase. The activity ratio of pyruvate kinase in (NH₄)₂SO₄-treated cells represented about 50% of that in the absence of the hormone. This difference may be related to glucagon-induced phosphorylation of pyruvate kinase.

KEY WORDS: • protein • hepatocytes • dihydroxyacetone • gluconeogenesis • glycolysis • pyruvate kinase • glucagon

¹ This work represents part of a doctoral dissertation submitted by B. Azzout to the University of Paris VI.

² This work was partially supported by a grant from the M.R.I. (83.C.0446), France.

³ To whom reprint requests should be sent at the address above.

Manuscript received 12 April 1984.

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