Hepatic metabolism of glucose, galactose, and lactate after milk feeding in newborn lambs.

The purpose of this study was to test the ability of the liver to efficiently clear substrates absorbed from the gastrointestinal tract after a feeding before entry into the systemic circulation. We placed a hepatic vein (HV) catheter in utero at 135-140 days gestation. The lamb was then allowed to deliver spontaneously, and additional catheters were placed in the portal vein (PV) and femoral artery (FA) at 1-3 days postnatal age. After at least 2 days recovery, lambs were fasted overnight at 4-10 days of age and then allowed to nurse ad libitum. There was significant hepatic glucose release during fasting and after 80 min postprandially. No net hepatic uptake of glucose was observed before or after feeding. PV galactose was significantly greater than FA and HV from 40 to 160 min after feeding (P less than 0.005). Hepatic glucose extraction was negligible in the fasted state (1 +/- 3%) and increased after feeding to 75 +/- 2% when PV galactose was less than 1.0 mM. There was a significant hepatic arteriovenous concentration difference of lactate (0.23 +/- 0.03 mM) and of oxygen (0.27 +/- 0.01 mM), which did not change significantly after feeding. The metabolic quotient for galactose increased significantly after feeding, such that galactose was the largest carbon contributor for postprandial hepatic carbon accretion. After a milk feeding, the newborn liver efficiently extracts galactose, lactate, and oxygen, but not glucose.