Mechanism of gluconeogenesis inhibition in rat hepatocytes isolated after in vivo hypoxia.

International audienceGluconeogenesis was studied in hepatocytes isolated from fasted rats submitted to 24 h of hypoxic exposure (inspired O2 fraction 0.1) or to room air. Hepatocytes from hypoxic rats compared with controls exhibited a lower gluconeogenic rate with lactate (5.1 +/- 0.3 vs. 7.2 +/- 0.3 mumol.min-1.g dry cells-1, P < 0.001) but not with dihydroxyacetone (9.1 +/- 0.3 vs. 9.4 +/- 0.4 mumol.min-1.g dry cells-1), suggesting involvement of the phosphoenolpyruvate-pyruvate cycle. Experiments with perifused hepatocytes from hypoxic and control rats showed a single relationship between phosphoenolpyruvate and glucose flux (JGlc) but two different curves when cytosolic oxalacetate was plotted against JGlc. The decreased phosphoenolpyruvate carboxykinase (PEPCK) activity in the hypoxic group (9.0 +/- 0.9 vs. 16.2 +/- 1.9 nmol.min-1.mg protein-1, P < 001) without change in the Michaelis constant further settled the involvement of this step. The significant decrease in PEPCK mRNA levels in livers from hypoxic rats led us to propose that in vivo hypoxic exposure inhibits gluconeogenesis at the PEPCK level by decreasing PEPCK gene transcription

Isolated rat hepatocyte metabolism is affected by chronic renal failure.

International audienceMetabolic changes due to chronic renal failure (CRF) were studied in isolated liver cells. In 14 CRF and 14 sham-operated rats, liver cells were isolated by the Berry and Friend method and incubated with various substrates in order to study gluconeogenesis, ureagenesis, ketogenesis, oxygen consumption as well as cytosolic and mitochondrial adenine nucleotide content. CRF rat hepatocytes exhibited a 25% to 45% decrease in gluconeogenesis and ureagenesis (P < 0.05) from all the tested substrates (lactate plus pyruvate, fructose, glycerol, dihydroxyacetone, alanine and glutamine for gluconeogenesis and alanine, glutamine, ammonia and ammonia plus ornithine for ureagenesis), while endogenous rates were unaffected. CRF did not alter ketone body production (acetoacetate and beta-hydroxybutyrate) from oleate or octanoate. In the presence of either oleate, lactate plus pyruvate or ammonia, oxygen uptake as well as cytosolic and mitochondrial total adenine nucleotides were unaffected by CRF, while the mitochondrial ATP/ADP ratio decreased (P < 0.001). Thus, this study of hepatocyte intermediary metabolism during CRF showed an alteration of only gluconeogenesis and ureagenesis pathways. Moreover, the association of normal oxygen uptake together with decreased mitochondrial ATP/ADP ratio suggest a possible increase in hepatocyte ATP demand during uremia