Liver glucose, glycogen and lipid synthesis in fed and 24-hour fasted rats soon after a pulse of [3-14C]pyruvate through the portal vein.

1. A pulse of [3-14C]pyruvate was given to rats through the portal vein and blood was collected at brief intervals from the inferior cava vein at the level of the suprahepatic veins. 2. In 24 hr fasted rats, the appearance of [14C]glucose in blood and blood glucose specific radioactivity were higher than in fed animals from the first minute after delivery of the tracer. At this time total radioactivity did not differ between the two groups. 3. After 5 and 20 min. liver radioactivity present in glycogen and glyceride glycerol was enhanced while in fatty acids it was reduced in fasted as compared with fed animals. 4. It is proposed that, in the fasted state, both glycogen and glyceride glycerol synthesis are predominantly gluconeogenic processes.