ABSTRACT
Intestinal ionic exchanges were studied in rat duodenal, jejunal and ileal ligated loops in response to different luminal saline loads: NaCl concentration varied from 150-0 mM, solutions being made isoosmotic with mannitol. The contact delay was 60 min. An exponential relationship was found between water, Na and Cl movements and the initial saline concentration. Maximal absorption was obtained with 150 mM NaCl, and was significantly higher in the duodenum than in the jejunum and ileum. The NaCl concentration for which water, Na, and Cl movements were null was approximately 70 mM NaCl in the duodenum and jejunum, 41 mM for Na and 18 mM for Cl in the ileum. The water efflux induced by the 0-mM NaCl test solution was maximal in the duodenum (1.5 +/- 0.2 ml/h) and decreased in the jejunum (0.8 +/- 0.1 ml/h) and ileum (0.3 +/- 0.1 ml/h) as did sodium, chloride and non-chloride anion efflux. These data support the functional heterogeneity of the small intestine regulating the water and ion exchange in response to luminal saline load, the main difference being connected with the efflux capacity of the mucosa, decreasing from the duodenum to the jejunum and ileum.
Subject(s)
Duodenum/metabolism , Ileum/metabolism , Jejunum/metabolism , Sodium Chloride/pharmacology , Animals , Bicarbonates/metabolism , Body Water/metabolism , Chlorides/metabolism , Duodenum/drug effects , Ileum/drug effects , Intestinal Absorption/drug effects , Jejunum/drug effects , Male , Mannitol , Osmolar Concentration , Potassium/metabolism , Rats , Rats, Sprague-Dawley , Sodium/metabolism , Sodium Chloride/administration & dosage , SolutionsABSTRACT
Sorbin is a newly isolated intestinal peptide that has been purified because of its ability to induce water absorption. The effects that sorbin and some synthetic peptides corresponding to its C-terminal sequence have on duodenal absorption of water, chloride, and sodium were studied in comparison with the effects of vasoactive intestinal peptide (VIP), [D-Ala,Met]-enkephalinamide (DAMA), and angiotensin II. The technique of an in situ ligated duodenal loop in the rat was used for all peptides. Under the experimental conditions used, a low basal secretion of water, chloride, and sodium was obtained; VIP induced an increase of the secretion, whereas DAMA induced an absorption, both in the nanomolar dose range. Angiotensin II and sorbin induced an absorption in the picomolar dose range. The most effective doses of sorbin peptides but not of angiotensin induced the lowest final concentrations of Na+ and Cl- obtainable without inducing secondary water secretion. All synthetic peptides containing the C-terminal heptapeptide of sorbin were active in the picomolar dose range. Contrary to angiotensin, they had no effect on blood pressure.
Subject(s)
Duodenum/physiology , Intestinal Absorption/drug effects , Peptides/pharmacology , Water-Electrolyte Balance/drug effects , Amino Acid Sequence , Angiotensin II/pharmacology , Animals , Blood Pressure/drug effects , Chlorine/metabolism , Enkephalin, Methionine/analogs & derivatives , Enkephalin, Methionine/pharmacology , Male , Molecular Sequence Data , Rats , Rats, Sprague-Dawley , Sodium/metabolism , Vasoactive Intestinal Peptide/pharmacology , Water/metabolismABSTRACT
The effect of bombesin (BBS) and gastrin releasing peptide (GRP) on gastric emptying was studied in conscious cats. This effect was measured simultaneously with antral motility. Acid and pepsin secretions as well as blood hormonal peptide release were additionally measured. A dual effect was observed. First, BBS and GRP slowed gastric emptying of liquids, while antral motility was decreased, then after 60 minutes of continuous intravenous infusion, antral motility returned to basal values and gastric emptying effect reversed. The mechanism of this peculiar action is independent of gastrin, pancreatic polypeptide, somatostatin and motilin release and most probably connected with a cholinergic stimulation induced by the peptides, the late predominance of which counterbalances the inhibitory effect of bombesin-like peptides on antral motility.
