Zonation of gluconeogenesis from lactate and pyruvate in the rat liver studied by means of anterograde and retrograde bivascular perfusion

Abstract

Gluconeogenesis from lactate and pyruvate and associated parameters were investigated in the bivascularly and hemoglobin-free perfused rat liver. The substrates were infused either via the portal vien (anterograd perfusion mode), via the hepatice vein (retrograde mode) or via the hepatic artery (anterograde and retrograde modes). The rates of lactate and pyruvate infusion were 10.3 and 3.5 ωmol min −1 g −1, respectively. The metabolic rates measured when the substrates were infused into the hepatic artery were referred to the cellular spaces accessible in each perfusion mode. The following results were obtained when the substrates were infused into the hepatic artery: (1) gluconeogenesis from lactate was equal to 2.08 ± 0.2 ωmol min −1 ml −1 in the retrograde mode and 1.33 ± 0.08 ωmol min − ml − in the anterograde mode ( P = 0.019); (2) gluconeogenesis from pyruvate was equal to 0.66 ± 0.11 ωmol min −1 ml −1 in the retrograde mode and 0.7 ± 0.11 ωmol min −1 ml −1 in the anterograde mode ( P = 0.75); (3) oxygen uptake increase with lactate was 1.75 ± 0.14 ωmol min −1 ml −1 in the retrograde mode and 1.05 ± 0.07 ωmol min −1 ml −1 in the anterograde mode ( P = 0.002); (4) oxygen uptake increase with pyruvate was equal to 0.59 ωmol min −1 ml −1 in the retrograde mode and 0.53 ± 0.05 ωmol min −1 ml −1 in the anterograde mode ( P = 0.75); ()5) pyruvate production from lactate was 0.28 ± 0.06 ωmol min −1 ml −1 in the retrograde mode and 0.39 ± 0.05 ωmol min −1 ml −1 in the anterograde monde ( P = 0.28); (6) lactate production from pyruvate was equal to 0.52 ± 0.05 ωmol min −1 ml −1 in the retrograde mode and 0.99 ± 0.08 ωmol min −1 ml −1 in the anterograde mode ( P < 0.001). Since only periportal cells are supplied with substrates when they are infused via the hepatic artery in retrograde perfusion, these results allow the conclusion that gluconeogenesis from lactate predominates in periportal hepatocytes. When pyruvate in the sole substrate, however, gluconeogenesis in periportal and perivenous cells presents no differences.