The effect of perfusate pH on respiration and glycolysis in the isolated rat liver perfused with an erythrocyte- and protein-free medium

Abstract

1. 1. An erythrocyte- and protein-free medium was used for perfusion of the isolated rat liver at 37 °C. When O 2 saturation was kept above 75% and perfusate flow above 40–50 ml/min, the liver respired maximally. Liver functions were normal as judged by respiratory rate, formation of glucose, lactic and pyruvic acid, lactic/pyruvic acid ratio, bile production and gross morphology. There was very little leakage of liver enzymes into the perfusate, but plasma proteins were secreted at a significant rate. 2. 2. CO 2 or Ca 2+ had no effect on respiration, whereas crude albumin had a slightly stimulatory effect. 3. 3. Respiration was strongly inhibited by H +, decreasing continuously with falling pH values between pH 8.0 and pH 6.7. 4. 4. The liver produced significant quantities of acid during the first 20–30 min of perfusion. This could be seen as a drop in the pH of perfusates buffered with 10–40 mM N-2-hydroxyethylpiperazine- N′-2-ethanesulfonic acid (HEPES). With bicarbonate (25 mM) as buffer in the presence of 5% CO 2, the buffering capacity was sufficient to maintain pH constant for at least I h. The total acid production was too great to be accounted for by lactic and pyruvic acid alone. 5. 5. The formation of lactic and pyruvic acid was strongly inhibited by H +. At pH 7.0, the rate of formation was only one-third the rate of pH 7.8. 6. 6. The parallel changes in glycolysis (lactic acid formation) and aerobic respiration with pH are in contrast to the inverse relationship characterized by the Pasteur effect and the Crabtree effect.