Refeeding after a fast in rats: effects on small intestinal enzymes.

The effect of resuming food intake after a period of starvation (refeeding) on the specific activities of selected rat intestinal enzymes was determined. The rate of weight gain was higher in refed animals than in control animals, without a difference in food intake. Fasting caused intestinal atrophy which reversed rapidly on refeeding. Fasting decreased the specific activities of sucrase, maltase, and galactokinase, but did not affect the specific activities of hexokinase, pyruvate kinase, or crypt thymidine kinase. Sucrase, maltase, hexokinase, pyruvate kinase, and thymidine kinase specific activities all rose above control values during refeeding. The overshoot in intestinal enzyme specific activities may help promote the rapid weight gain observed in refed rats and is an integral part of the total adaptation to fasting and refeeding.