Abstract
Alterations in ileal epithelium and villus structure during L-tryptophan(Trp) exposure were studied in vivo in rat ileal loops. The mucosal surface of 20 cm loops was infused for 2.5 and 30 min with isotonic Tris buffer ( pH 7.3 ) and NaCl( 140 mM ) containing either 20 mM Trp, 20 mM glycine ( Gly ) or no amino acid, phenol red was used to monitor water transport. Horseradish peroxidase ( HRP ) was added in the lumen or i.v. 5 min prior to the experimental treatment. Tissue was then examined by light and electron microscopy. After 2.5 min in Trp there were numerous large vacuoles seen in the serosal side of the apical epithelial cells. The vacuoles appeared as if derived from basolateral plasma membrane; many vacuoles were labeled with HRP injected i.v. prior to luminal Trp and there was detachment of membrane from the basal lamina. By contrast,the mucosal side of the cells was unaffected and the barrier to luminal HRP was intact. Villi and epithelium in Gly and buffer controls were unaltered. After 30 min of luminal Trp, there was marked extrusion of epithelium from the apical villus region and the luminal permeability barrier to HRP was lost. Net water transport was also inhibited by Trp( Trp=.190±.09 ul/minxcm;Gly=1.03±.11 p<.01;buffer=.947±.09 p<.01). Overall, our observations indicate that Trp alters the ileal apical epithelium and induces water malabsorption. The transport change may be linked to intemalization of basolateral membrane, thereby removing transport proteins from their normal loci.
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Teichberg, S., Wapnir, R., Zdanowicz, M. et al. 740 STRUCTURAL ALTERATIONS IN ILEAL EPITHELIUM INDUCED BY L-TRYPTOPHAN. Pediatr Res 19, 234 (1985). https://doi.org/10.1203/00006450-198504000-00770
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DOI: https://doi.org/10.1203/00006450-198504000-00770