The activity of 19 liver enzymes as well as the level of activity of a lesser number of
enzymes in brain, kidney and heart tissue was measured in C57BL/6 mice at various ages between
birth and 35 days. Several enzymes were present at significant levels in the liver at earlier ages than
reported for rat liver. The time course of the development, the magnitude of the charges and the
direction of the changes are often significantly different from the profiles observed in rat tissues,
thus the mouse may respond differently than other species to dietary alterations and/or hormonal
stimulations during the developmental period.