Changes in fructose-2,6-bisphosphate levels after glucose loading of starved rats.

Fructose-2,6-bisphosphate levels in freeze-clamped livers of starved rats were 0.5 nmol/g liver. Oral administration of 1 g glucose per kg body weight to starved rats increased glycogen levels from 4 mg/g liver to 13.5 mg/g in 2 hr but did not significantly alter fructose-2,6-bisphosphate levels. The low level of this effector is consistent with an active gluconeogenic process and the results support the hypothesis that carbon atoms for glycogen synthesis can be derived from 3-carbon precursors via this pathway, even in the presence of glucose.