Comparison of blood glucose and liver glycogen of larval and adult frogs (Rana pipiens).

Blood glucose levels are lower in tadpoles than adults. Transition to adult levels occurs during the later stages of metamorphosis, but the rise is interrupted by a brief decline in blood glucose at the beginning of metamorphic climax. Liver glycogen rises from 4.6% to 8% during larval life, falls to 1.7% at the beginning of metamorphic climax then returns to 5-770 during late climax and in the frog. Possible mechanisms responsible for the differences in carbohydrate regulation in larval and post metamorphic amphibians, and the biological significance of the differences are briefly discussed.