Determination of alpha(1)-proteinase inhibitor by a new enzyme linked immunosorbant assay in feces, serum and an enterocyte-like cell line

Although alpha (1)-proteinase inhibitor (alpha (1)-PI), the main serine pro teinase inhibitor in human plasma, is predominantly liver-derived, the proo f of fecal alpha (1)-PI is a maker for intestinal protein loss. Furthermore , alpha (1)-PI is synthesized locally by human intestinal epithelial cell l ines (e. g. Caco-2). Therefore, we investigated the diagnostic value of a n ew enzyme-linked immunosorbent assay (ELISA) to detect alpha (1)-PI in seru m, feces, and Caco-2 supernatants in comparison with radial immunodiffusion (RID). alpha (1)-PI concentrations assessed by ELISA were on an average 30 % higher than those measured by RID. Only the ELISA system detected alpha ( 1)-PI in supernatants of Caco-2 cells. Our data imply first that this ELISA system is more sensitive to assess alpha (1)-PI than other methods, and se cond that it obviously determines locally synthesized alpha (1)-PI which ca n not be liver-derived. However, further examinations are necessary to dist inguish between enterocyte-derived or systemic alpha (1)-PI and its diagnos tic relevance in bowel disease.