Galactose metabolism in suckling and adult isolated rat hepatocytes

The metabolism of galactose during the postnatal developmental period has been examined in isolated parenchymal cells of livers from fasted rats aged 7, 14, 21, 28, and 42 days, by measuring the disappearance of 1 and 4 mM 1-[14C]galactose from the incubation media as well as [14C]galactose conversion to [14C]glucose and [14C]lactate and oxidation to [14CO2]. Cells from 7- and 14-day-old suckling animals consistently utilized galactose more rapidly (4 times greater) than those of adult. Hepatocytes of suckling rats also converted greater amounts of galactose to glucose and oxidized galactose 2-3 times faster than the adult. The conversion to glucose by suckling cells occurred with minor recycling of labeled C-1 galactose to C-6 of glucose. A comparison with [1-14C]glucose as substrate showed that oxidative rates by the young cells were 3 times faster for galactose than for glucose. This was not due to the presence of a direct galactose oxidative pathway as assessed by the [14CO2] yield from C-1 and C-2 labeled galactose. Incubation of hepatocytes with galactose appeared to augment the production of glucose from endogenous precursors, 33 nmoles/mg cells in 30 min. The enhanced glucose output from endogenous sources in isolated suckling hepatocytes incubated with galactose contrasts with the sugar's suppression of glucose output observed in isolated perfused liver even though galactose metabolism in both preparations are similarly greater in the suckling than in the adult.