EFFECTS OF ARTERIAL-PORTAL GLUCOSE DIFFERENCE ON GLUCONEOGENESIS FROMLACTATE IN THE ISOLATED BIVASCULAR-PERFUSED RAT-LIVER

The effects of arterial-portal glucose difference on the gluconeogenes is from lactate were studied using the bivascular perfused liver isola ted from the fasted rat. The liver was cyclically perfused at flow rat es of 14 ml/min from the portal vein and of 7 ml/min from the hepatic artery with the total volume of 35 ml of perfusion medium containing 2 mM glucose, 3 mM lactate and (U-C-14)-lactate for 20 min. Glucose was infused at a rate of 27.75 mumol/min into the arterial cannula (A-exp eriment) or the portal cannula (P-experiment), making each arterial-po rtal glucose gradient of + 3.96 mM (arterial glucose > portal glucose) and -1.98 mM (arterial glucose < portal glucose) throughout the exper iment. Perfusate lactate concentration was lower in A-experiment than in P-experiment (1.40 +/- 0.25 vs 1.93 +/- 0.23 mM at 20 min, mean +/- SD, p < 0.05). Incorporation of radioactivity from (U-C-14)-lactate in to glucose carbon 1 in perfusate was 5.7 +/- 0.8% of total radioactivi ty per 20 min in A-experiment vs 2.8 +/- 0.6%/20 min in P-experiment ( p<0.01). These results suggest that the arterial-portal glucose differ ence is an important factor to regulate the hepatic gluconeogenesis.