Carbachol but not forskolin can increase mucosal to serosal
transport of intact protein in rat ileum in vitro.
Bijlsma, Pieter B., Amanda J. Kiliaan, Greet Scholten, Martine Heyman,
Jack A. Groot, and Jan A. J. M. Taminiau.
Dept. Pediatr. Gastroenterology and Nutrition, Acad. Medical
Centre, 1105 AZ Amsterdam and Dept. Exp. Zoology. University of
Amsterdam. 1098 SM Amsterdam. The Netherlands. INSERM U 290,
H[circumflex]opital St. Lazare, Paris, France
APStracts 3:0095G, 1996.
The effects of the secretagogues forskolin and carbachol on protein
uptake in isolated ileum of rats were studied. The mucosa to serosa
transport of horseradish peroxidase (HRP, MW 40 kD) was measured in
Ussing chambers, and afterwards tissues were processed for electron
microscopy. In the absence of secretagogues, the flux of
enzymatically active HRP was 5 pmoles/cm2.h at a mucosal
concentration of 10 [mu]M. Electron micrographs showed vesicles
filled with active HRP in enterocytes but no HRP-activity in
intercellular spaces. Forskolin decreased HRP-activity in the cells.
Carbachol increased the amount of HRP-filled vesicles in enterocytes
and induced HRP-filling in some intercellular spaces and tight
junctions in the upper parts of the villi. The transepithelial flux
of intact HRP increased more than 2.5 fold. This effect was
suppressed by atropine. We conclude that cholinergic activation can
increase the uptake of intact protein via endocytosis and the trans
-epithelial passage by the induction of a diffusional paracellular
pathway. We speculate that the increased transport of intact protein
through the intestinal barrier may influence immunological
sensitization to food-allergens.
Received 24 June 1995; accepted in final form 11 March 1996.
APS Manuscript Number G273-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96