Effect of Protonated 2,4,6-Triaminopyrimidine, A “Tight Junction blocker,” on Intestinal Transport in Dog Ileum In Vivo
1977; Elsevier BV; Volume: 72; Issue: 4 Linguagem: Inglês
10.1016/s0016-5085(77)80155-8
ISSN1528-0012
AutoresGuenter J. Krejs, Leonard L. Seelig, John S. Fordtran,
Tópico(s)Clinical Nutrition and Gastroenterology
ResumoPrevious in vitro experiments suggest that protonated 2,4,6-triaminopyrimidine (TAP+) inhibits passive Na+ movement across tight junctions of various epithelial tissues.So far no evidence has been found that T AP+ interferes with other mucosal transport processes.Because blockage of the tight junctions would be a promising tool in studying intestinal transport physiology, the effect ofTAP+ was investigated in the dog ileum in vivo.When TAP+ was added to a sodium-free mannitol solution, the transepithelial sodium diffusion potential was significantly decreased (60% inhibition with 34 mM TAP+); this would be expected if TAP+ inhibited Na+ permeation through tight junctions.However, TAP+ was also found to diminish Na+ and CI-absorption.Furthermore, TAP+ increased unidirectional Na+ flux from plasma to lumen; this is opposite to the expected result of tight junction blockage.In addition, TAP+ reduced glucose, fructose, and xylose absorption by about 50%.In ileal loops exposed to cholera toxin, T AP+ enhanced secretion by a rate equal to the rate by which it reduced absorption in loops not exposed to cholera toxin.All changes induced by TAP+ approached normal within 4 hr of its removal from the perfusate.TAP+ did not cause any mucosal damage that could be detected by protein leakage or by light microscopy.These studies show that TAP+ has many effects on intestinal transport processes that cannot be explained on the basis of tight junction blockage.
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