The influence of the position of the oxygen dissociation curve on oxygen-dependent functions of the isolated perfused rat liver

Isolated rat livers were perfused with fresh and 2,3-DPG (2,3-diphosphoglycerate)-depleted human crythrocytes at different levels of hypoxia. The meanP ₅₀ values of the measured actual oxygen dissociation curves (O.D.C.) were 24.5 and 18 mm Hg. No changes in flow rate and perfusion pressure occurred under the different experimental conditions. It was shown that an advantage or disadvantage of a shift of the O.D.C. depends on the degree of hypoxia, as reflected in the venous \(P_{O_2 } \) . Perfusions with fresh erythrocytes showed higher venous \(P_{O_2 } \) values during normoxia or moderate hypoxia and lower venous \(P_{O_2 } \) values at severe hypoxia. A cross-over point was found at a \(P_{O_2 } \) in the portal vein of 36 mm Hg. The disadvantage of perfusions with fresh erythrocytes at severe hypoxia was also reflected in higher cytoplasmatic and mitochondrial redox levels. Using bile flow rate as an indirect measure for the rate of hydroxylation-dependent O₂ consumption a favourable effect of perfusion with fresh erythrocytes was found at a \(P_{O_2 } \) in the portal vein of 100 and 40 mm Hg.