Effects of fasting on intestinal transfer of sugars and amino acids in vitro.

1. Transfer of sugars, amino acids and fluid and metabolism of glucose were studied with everted sacs of small intestine prepared from fed and 3-day fasted rats.2. In the absence of glucose there was some evidence for increased intestinal transfer of sugars and amino acids in fasted animals. In the presence of glucose there was in general decrease in transfer of amino acids and fluid.3. In fasted animals glucose transfer was reduced except in the lower ileum, and there was a general reduction in glucose metabolism.4. Because of the large reduction in gut weight in fasted animals, expressing transfer on a weight basis is considered not to be a valid procedure in studying the effects of fasting on intestinal transfer.5. The results have been discussed in relation to effects of fasting on energy availability, efficiency of transfer mechanisms, permeability of the intestine and the value of in vitro methods in the study of physiological absorption.