Effects of quantity and quality of dietary protein on the jejunal absorption activities for L-leucine and glycylglycine in rats.

Abstract

In order to study the variability of intestinal transport systems for amino acid and peptide, the effects of quantity and quality of dietary protein on the absorption of L-leucine and glycylglycine were investigated in situ in the rat jejunum. The absorption activities for both amino acid and dipeptide changed in a similar manner in response to the dietary levels of casein ; decreasing below 10%, remaining nearly constant between 10 and 50%, and increasing above a 50% casein level. Similar results were obtained with wheat gluten. At an equal dietary protein level (equivalent to 10% casein), the absorption activities for L-leucine and glycylglycine in rats fed with a zein or gelatin diet were lower than those in animals fed with a casein or gluten diet. A high correlation was observed between the absorption activity for L-leucine and that for glycylglycine in all dietary groups. The results clearly indicate that jejunal absorption activity for glycylglycine could be altered in parallel with that for L-leucine by changes of the quantity and quality of dietary protein.