Uptake of lactate by the liver: effect of red blood cell carriage

Abstract

Multiple-indicator dilution experiments with labeled lactate were performed in the livers of anesthetized dogs. A mixture of51Cr-labeled erythrocytes, [3H]sucrose, andl-[1-14C]lactate or a mixture of51Cr-labeled erythrocytes, [14C]sucrose, andl-[2-3H]lactate was injected into the portal vein, and samples were obtained from the hepatic vein. Data were evaluated using a model comprising flow along sinusoids, exchange of lactate between plasma and erythrocytes and between plasma and hepatocytes, and, in the case ofl-[1-14C]lactate, metabolism to H[14C][Formula: see text]within hepatocytes. The coefficient for lactate efflux from erythrocytes was 0.62 ± 0.24 s−1, and those for influx into and efflux from hepatocytes were 0.44 ± 0.13 and 0.14 ± 0.07 s−1, respectively. The influx permeability-surface area product of the hepatocyte membrane for lactate ( P in S, in ml ⋅ s−1 ⋅ g−1) varied with total flow rate ( F, in ml s−1 ⋅ g−1) according to P in S = (3.1 ± 0.5) F+ (0.021 ± 0.014). Lactate in plasma, erythrocytes, and hepatocytes was close to equilibrium, whereas lactate metabolism was rate limiting.