1. Feeding a high-glucose diet to weanling rats showed that high hepatic glucokinase activities could be induced at 18 days of age, i.e. 2 days after development of the enzyme begins. 2. The normal development of glucokinase activity can be retarded by weaning rats on to carbohydrate-free, high-fat and high-protein diets. 3. Precocious development of the enzyme before 16 days of age cannot be induced by oral glucose administration. 4. It is concluded that the ability to synthesize glucokinase develops very rapidly and that the nature of the diet determines the normal developmental pattern.
