CHARACTERIZATION AND QUANTIFICATION OF PLASMA-PROTEINS EXCRETED IN FECES FROM HEALTHY HUMANS

Faecal plasma protein loss was studied in 38 healthy adults. Using cro ssed immuno-electrophoresis and single radial immunodiffusion the most frequently found proteins were alpha(1)-antitrypsin, IgA, alpha(1)-an tichymotrypsin (found in 97, 92, and 84% of subjects), prealbumin and IgM (both found in 55%). The major plasma proteins, albumin and IgG, w ere found in 37 and 13% of subjects, respectively, and in trace amount s only. alpha(2)-macroglobulin could not be detected. There was no rel ation between the presence of proteins in faeces and their plasma conc entration. When added to faeces, alpha(1)-antitrypsin, alpha(1)-antich ymotrypsin, and prealbumin were resistant to incubation (37 degrees C, 48 h), whereas albumin, IgG, IgM, and IgA were rapidly degraded (with in 8-24 h). Some IgA was bound to secretory component, indicating ente ric secretion. alpha(2)-macroglobulin was semi-resistant to degradatio n, but its passage to the intestinal lumen may have been prevented by its molecular size. In conclusion, resistance to degradation, enteric secretion, and low molecular weight are the primary factors which favo ur the excretion of plasma proteins in faeces. The technique used in t his study allows further studies in patients with inflammatory changes and protein-losing enteropathy.