Utilization of Fat and Glycerol for Glycogenesis by the Neonatal Rat

Hepatic glycogenesis from fat and glycerol has been studied in the fasted rat during development. Administration of either olive oil or glycerol resulted in marked hepatic glycogenesis in 5- to 10-day-old animals; this response was diminished in weaned rats and was almost absent in animals less than 48 hours old. The incorporation of 14C-glycerol into hepatic glycogen was greater in 9-day-old neonatal rats than in weaned animals. Although glycerol kinase activity was low in liver of animals less than 48 hours of age, these young animals readily converted 14C-glycerol into 14CO2. Our results indicate that glycerol is utilized via different pathways depending on the age of the animal. Hepatic glycogenesis, following fat administration, in the 5- to 10-day-old rat can be explained on the basis of increased utilization of triglyceride-glycerol for glyconeogenesis during this period of neonatal life.