EFFECT OF SAPONIN ON THE TRANSMUCOSAL PASSAGE OF BETA-LACTOGLOBULIN ACROSS THE PROXIMAL SMALL-INTESTINE OF NORMAL AND BETA-LACTOGLOBULIN-SENSITIZED RATS

The ability of saponins and glycoalkaloids to permeabilise the mammali an intestinal barrier has been previously demonstrated in vitro, leadi ng to the hypothesis that membranolytic saponins may facilitate transf er to the tissues of otherwise excluded macromolecules. An enhanced up take of, for instance, potentially allergenic species from the lumen i s one of the factors that may affect the induction of food allergy, an d its presentation in already sensitised individuals. In the experimen ts described here, an increase in the transmucosal uptake of the milk allergen beta-lactoglobulin (beta LG) was assessed in non-sensitised a nd sensitised Brown Norway rats in the presence of Gypsophila saponin. Isolated jejunal loops were exposed in vivo to either beta LG followe d by saponin, saponin followed by beta LG or the two compounds simulta neously. Portal vein blood samples were collected and assayed for beta LG and rat mucosal mast cell protease (RCMP II) activity. Mucosal tis sue was also examined histologically and assayed for histamine content . Sham-operated animals, exposed to physiological buffer alone, were i ncluded as controls and beta LG measurements corrected for this compon ent which was negligible. No transfer of beta LG occurred in the absen ce of saponin in non-sensitised rats, whereas a significant enhancemen t was observed in the presence of saponin. beta LG was detected in the portal circulation of sensitised rats exposed to beta LG alone; howev er addition of saponin to the intestinal lumen further enhanced this u ptake, possibly by an independent mechanism. Histological examination of the mucosal epithelium exposed to saponin revealed damage, especial ly at the villus tips. Mucosal histamine and serum RCMP II concentrati ons were consistent with the differences observed between sensitised a nd non-sensitised animals. It is concluded that exposure to food const ituents capable of permeabilising the mucosal epithelium may increase the risk of sensitisation to dietary antigens. (C) 1997 Elsevier Scien ce Ireland Ltd.