Small Intestinal Dipeptidases and Disaccharidases in Uraemic Rats on a Low Protein Diet

Abstract

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 ohgopeptides because of the type of nutrition given.

Small Intestinal Peptidases and Disaccharidases in Rats with Acute Uremia

“…The activities of the two other peptidases were also increased, but the difference did not reach statistical significance. The in creased peptidase activity in uremic rats is in line with several studies on intestinal dipeptidase activity in chron ically uremic rats fed with an unrestricted protein diet [3,5,25], In chronically uremic rats fed a low-protein diet the dipeptidase activities were reduced to the same level as in normal rats [21]. Total parenteral nutrition further de creased the dipeptidase activity [21].…”

“…4). In chronic uremia both increased and decreased activity of various disaccharidases has been demonstrated [2,3,5,21]. The different results of the acute and chronic uremia could also be due to different composition of the diets and to different length of the observation periods [22][23][24], The short uremic period in our study, compared to that of chronic uremia, could be one reason for the unaltered disaccharidase activity in the uremic group in our study.…”

Mucosal Peptide Hydrolase and Brush-Border Marker Enzyme Activities in Three Regions of the Small Intestine of Rats with Experimental Uraemia

“…Previous literature regarding direct measurement of amino acid or peptide absorption from the small intestine in uraemia is scant [ l 1, 14, 151. As mucosal brush-border and cytosolic peptidases are believed to be functionally important during the terminal digestion of protein, and are also reported to correlate well with morphological changes [ 161, quantification of these enzymes has been used previously to give an indication of potential malabsorption of protein in uraemia [5,[17][18][19][20][21]. Due to the problems of obtaining human tissue, virtually all work of this type has been performed with tissue provided by animal models of the human condition.…”