Galactose and glucose metabolism by cultured hepatocytes: responsiveness to insulin and the effect of age.

Age changes in utilization of glucose and galactose were studied in primary cultures of rat hepatocytes. (1) With increasing age of donor from 2 to 10 weeks, the rate of galactose utilization fell while that of glucose utilization increased from a negative value (net production) to a level approximately double that of galactose. Glucose production could account for about 80% of the galactose taken up by cells from 2- to 3-week-old rats. (2) With increasing time of culture there was a fall in galactose utilization and an increase in glucose utilization comparable to the changes with increasing age in vivo. (3) The change in utilization of each sugar was independent of the change in utilization or availability of the other. It is suggested that the switch from galactose to glucose as the preferred substrate in vivo is not determined by dietary availability of these hexoses. (4) The increased utilization of glucose by cells of older animals was associated with a decrease in responsiveness to the glycogenic action of insulin. The change in responsiveness was not due to a decrease in insulin binding capacity of the cells.