Intestinal brush border membrane structure and function: effect of early postnatal undernutrition

Effect of sulfasalazine on adaptive and functional changes in intestine of normal and protein-calorie-malnourished rats

The effects of sulfasalazine (500 mg/kg body weight daily for 35 days) and its subsequent recovery for another 35 and 65 days have been investigated on the intestinal uptake of certain end-product nutrients, viz. glucose, leucine, alanine, and calcium, in normal and protein-calorie malnourished (PCM) male albino rats. Sulfasalazine administration caused a reduction in body weight in PCM animals, while intestinal weight and length as well as protein and nucleic-acid contents were reduced in both normal and PCM animals. Serum proteins also showed a decrease in PCM rats. PCM rats showed elevated levels of glucose, amino acids, and calcium uptake by the intestinal segments, but sulfasalazine feeding inhibited the uptake of nutrients both in normal-fed and malnourished animals. All these changes were found to be reversible after the withdrawal of drug treatment. Sulfasalazine caused a decrease in the Na(+)-dependent (active) glucose uptake as well as the Na(+)-independent (passive) process. The kinetic parameters of glucose uptake indicate that the drug might interfere with the transport/carrier protein of these nutrients, because reduction was observed in maximum uptake velocity (Jmax) of these systems without any change in the affinity constant (Kt).

Effect of early postnatal long-term fasting on the development of peptide hydrolysis in chicks

1. Early development of peptide hydrolysis in the digestive tract was investigated in experiments with fasted and fed ad lib. chicks during the first decade of postnatal period. 2. Pancreatic carboxypeptidase A (CPA) activity was maximal at the moment of hatch. On the second day CPA activity considerably diminished in starved and fed animal groups; further starvation (3-4 days) led to the significant increase of CPA total and specific activity, whereas the amount of enzyme in pancreas of fed chicks was rather low. 3. Aminopeptidase (AP) activity of the small intestinal surface was less sensitive to starvation. The increase of activity in all intestinal parts was observed only on the 4th day of fasting. The most sensitive to starvation were dipeptidases. Changes in their activity (2-fold increase) were detected after 24 hr of starvation. 4. The formation of specific physiological proximo-distal gradient of intestinal exopeptidase activities began only after the moment of the first feeding. 5. This gives evidence that the development of peptide hydrolysis depends not only on the age of the animal but also on the normal physiological beginning of the process of exogenous nutrition.

Adaptive response of ileal mucosa to malnutrition in the rat: role of polyamines

Mucosal disaccharidases and ornithine decarboxylase activities were measured in malnourished, preweaning (19 days), post weaning (24 days) and young adult (37 days) rats. Malnutrition resulted in decreased body weight, intestinal weight, DNA and protein content. Mucosal Prot/DNA ratios were elevated in the ileal segments of the 24 and 37 day rats. Preweaned malnourished rats had significantly enhanced lactase specific activity in both jejunal and ileal segments. Adult malnourished rats showed enhanced jejunal lactase and sucrase activities which were not accompanied by elevated ornithine decarboxylase values. Mucosal sucrase and ornithine decarboxylase specific activities were significantly elevated in the ileal segment of the 24 and 37 day old malnourished rats. Studies of adult rats showed that these increased specific activities were located in the mature enterocytes at the villus tip, and persisted during a 24 h diurnal cycle. DFMO administration for 4 days completely inhibited mucosal ornithine decarboxylase and abolished the rise of ileal sucrase activity. We concluded that the intestinal response to reduced food intake is age related and differs in the jejunum and ileum: ornithine decarboxylase and polyamines are involved in ileal adaptation to malnutrition in postweaned and adult rats.

Effect of undernutrition and hormone treatments on the absorption of proteins in suckling rat intestine

The absorption of 125I-labeled BSA and gamma-globulin was significantly (P less than 0.01) elevated in UN pups compared to the controls. Administration of pharmacological doses of cortisone, thyroxine, and insulin markedly (P less than 0.001) reduced the absorption of BSA and gamma-globulin in UN pups. There was no significant difference in the binding of 125I-labeled BSA and gamma-globulin to microvillus membrane in the control and experimental animals. However, the degradation of labeled BSA and gamma-globulin by luminal content was considerably higher (55-70%) in controls compared to UN pups. This suggested that observed increase in the absorption of proteins in nutritionally deprived pups was unrelated to their binding to the microvillus surface but presumably it is a consequence of reduced luminal degradation together with delayed maturational development as suggested by the pattern of brush border enzymes in the UN intestinal tissue.