Gastrointestinal uptake of macromolecules.

Although the majority of dietary proteins undergo extensive digestion, small, nutritionally insignificant amounts of food proteins appear to cross the gastrointestinal mucosa intact. Experiments in a variety of allergic models has demonstrated that exposure of the gastrointestinal mucosa to the intact allergen leads to an anaphylactoid reaction. To examine the uptake of immunologically intact protein across the gastrointestinal epithelium, the mucosal to serosal movement of bovine serum albumin was measured in stripped gastric and intestinal mucosa mounted in modified Ussing-type chambers. Studies demonstrated that both gastric and intestinal mucosa are capable of actively transporting intact dietary proteins. In the intestine, the transport of intact molecules across the epithelium is a saturable, energy dependent process which utilizes the microtubular network and is regulated by the enteric nervous system. Transport across gastric mucosa is also dependent upon the microtubular network and is energy dependent.