Intestinal Assimilation of a Tetrapeptide in the Rat

Concentration and pH dependency of α-methyldopa absorption in rat intestine

“…The experimental technique was adapted from that of Smithson & Gray (1977) for the perfusion of the rat small intestine. Male Sprague Dawley rats, 200-300 g, were fasted for 48 h but water was freely available.…”

Abrupt Induction of a Membrane Digestive Enzyme by Its Intraintestinal Substrate

“…Thus, substrates such as the high-affinity tetrapeptide Gly-Leu-Gly-Gly or the peptide analog LeuNA appear to act rapidly and specifically, presumably by virtue of their interaction with AOP at the intestinal lumen-membrane interface to enhance the intracellular de novo synthesis of AOP. Studies of Gly-Leu-Gly-Gly hydrolysis in the rat jejunum have shown that its hydrolytic products in vivo are glycine, leucine, and the dipeptide Gly-Gly (2). Because the dipeptide product may be the inducer of AOP synthesis, pulselabeling experiments were carried out as described except that rats were perfused with a mixture of glycine, leucine, and Gly-Gly (2 mM each).…”

“…The question of whether this is a general phenomenon of substrate-hydrolase regulation for nutrients present- Trypanosomatid protozoa, including human pathogens of the genera Leishmania and Trypanosoma, are dependent on an exogenous supply of preformed purines because they are incapable of de novo purine synthesis (1). Knowledge of the mechanisms by which the organisms acquire or "salvage" these essential nutrients is therefore of significance in understanding the host-parasite relation and may lead to improved chemotherapeutic strategies against these parasites of public health importance (2).…”

“…Male Sprague-Dawley rats, paired by age and weight (200 to 300 g) and fed a protein-deficient diet (6) for 12 days, were anesthetized, and jejunal loops (25 cm long) were isolated and cannulated as described (2). The intestinal loop of the paired rats was simultaneously perfused for 30 minutes with 150 mM NaCl conta.iing either 2 mM L-Gly-Leu-Gly-Gly or the equivalent amino acid solution (6 mM glycine and 2 mM L-leucine; control).…”

Intestinal brush border aminooligopeptidases: cytosol precursors of the membrane enzyme

“…The intestinal membrane aminooligopeptidases are integral membrane proteins located at the luminal surface of the small intestinal cell. These digestive hydrolases are probably transmembrane proteins (Louvard et al, 1976) whose active site is available at the lumen-cell interface to ensure surface hydrolysis of oligopeptides of four to six amino acid residues which cannot be assimilated intact across the intestinal surface membrane (Smithson & Gray, 1977). Despite the importance of these enzymes for protein digestion, their intracellular site of synthesis, mode of intracellular translocation, and mechanism of membrane insertion are unknown.…”