Serum protein content of rat small-intestinal mucus

This investigation was performed to determine whether serum proteins which might contribute to mucosal protection are present in rat small intestinal mucus. Rats were fed an elemental diet, their small intestines removed, perfused, everted, and the surface mucus gently collected. Mucus was centrifuged to express its aqueous component (sol), whose serum protein content was analyzed by immunodiffusion in agarose gel. Immunoglobulins G and A were present in intestinal mucus sol; however, M and E could not be demonstrated. Serum albumin was present in mucus sol, but could be detected only following luminal perfusion with protease inhibitors. Although the role of serum albumin in intestinal mucus function is not clear, the presence of immunoglobulins G and A may contribute to the protective role played by mucus in the small intestine.