Small intestinal dipeptidases and disaccharidases in uraemic rats on a low protein diet

Small intestinal dipeptidases (substrate: glycyl-L-leucine, L-methionyl-L-methionine, and L-alanyl-L-proline) were determined in uraemic and sham-operated rats given normal protein diet (24%), low protein diet (6%), and total parenteral nutrition for 10-14 days. Disaccharidases (substrate: maltose, sucrose, trehalose, and lactose) were measured after normal and low protein diet orally. Glycyl-L-leucine and L-methionyl-L-methionine splitting activities were increased on normal protein diet but decreased after low protein feeding in uraemic rats. Parenteral nutrition further lowered the enzyme activity. L-Alanyl-L-proline dipeptidase activity showed an inverse relation to protein intake with the highest values after parenteral nutrition. Lactase increased in uraemic rats after low protein feeding and was the only disaccharidase to be affected by the nutritional change. It is suggested that the changes of the intestinal dipeptidase activities in uraemia are adaptive to variation in the luminal content of di- and oligopeptides because of the type of nutrition given.