The Responses of Rat Intestinal Brush Border and Cytosol Peptide Hydrolase Activities to Variation in Dietary Protein Content DIETARY REGULATION OF INTESTINAL PEPTIDE HYDROLASES

Abstract

AB STR A CT The effects of variation in dietary protein content on small intestinal brush border and cytosol peptide hydrolase activities have been investigated.One group of rats was fed a high protein diet (55% casein) and another group was fed a low protein diet (10% casein). After 1 wk, brush border peptide hydrolase activity (L-leucyl-P-naphthylamide as substrate) and cytosol peptide hydrolase activity (L-prolyl-L-leucine as substrate) were determined in mucosae taken from the proximal, middle, and distal small intestine. As judged by several parameters, brush border peptide hydrolase activity was significantly greater in rats fed the high protein diet when data for corresponding segments were compared. In contrast, no significant difference was seen in cytosol peptide hydrolase activity.In a second study, brush border and cytosol peptide hydrolase activities were determined in the proximal intestine by utilizing an additional three peptide substrates: L-leucyl-L-alanine, L-phenylalanylglycine, and glyCyl-L-phenylalanine. Sucrase, maltase, and alkaline phosphatase activities were also determined. As before, brush border peptide hydrolase activities were significantly greater in rats fed the high protein diet. However, activities of the nonproteolytic brush border enzymes did not vary significantly with diet. In contrast to the results obtained with L-prolyl-L-leucine as substrate for the cytosol enzymes, cytosol activity against

The adaptation of digestive enzymes to the diet : Its physiological significance

“…One of the first effects that diet has on the development of these enzymes is seen during fasting which causes brush border activities in the rat to decrease while the cytoplasmic activities increase (Kim et al, 1973) ; this would imply that the former enzymes are adaptive. Nicholson, Mc Carthy and Kim (1974) Deren, Broitman and Zamcheck, 1967 ;Stifel et al, 1968). The results obtained on the chicken (Siddons, 1972 ;Blum, Gauthier and Guillaumin, 1979) (1973) and studied by several authors (Borgstrbm and Erlanson, 1973 ;Borgstr6m, 1977 ;Rietsch et al, 1977).…”

“…According to Snook (1974) or from 13 to 88 p. 100 (Scharrer, 1972) causes a significant augmentation of the enzymatic activities or of amino acid absorption, but has no effect on animal growth. On the contrary, when the protein supply is lower than the requirement, growth is affected (Nicholson, Mc Carthy and Kim, 1974). The latter authors showed that, intake being equal, the weight gain of rats fed a 55 p. 100 casein diet was significantly higher than that of rats fed a 10 p. 100 diet.…”

Cholestyramine and Bile Diversion Lower the Aminopeptidase Activity in the Intestinal Brush Border Membrane of Rats.

“…With this mucosal homogenate, activities of three enzymes, contents of protein, and DNA were determined. Aminopeptidase activity was measured using leucine-p-nitroanilide as a substrate (15) in the presence of 0.5 mM PHMB, a known inhibitor of the cytosolic peptidases (16). Sucrase activity was measured using sucrose as a substrate (17) and the amount of glucose released was measured by Glucose-B-Test.…”

Intestinal brush border membrane enzyme activities of rats fed chemically defined diets containing oligopeptides or amino acids as the nitrogen source.

“…These disaccharidases have been investigated by Deren et al [5] and others [6,7]. Amnnopeptidase activity has been examined by Nicholson et al [8] in rats fed high-protein and low-protein diets. However, the relationship between dietary oligopeptides and aminopeptidase or cytosol peptidase activities remains unclear.…”