Digestion of milk proteins was studied in short-bowel patients. After ingestion of water, purified beta-lactoglobulin (beta-Ig), or skim milk, effluents were collected at the stoma. The flow rate of the effluent peaked in the first 30-min period after ingestion and returned to the basal value within the first 60 min. After milk ingestion 1) the nitrogen concentration of effluents peaked in the first 30 min, 2) SDS-polyacrylamide gel electrophoresis and Western blot indicated the presence of beta-Ig and alpha-lactalbumin (alpha-lac) in jejunal effluents but only during the first 30 min whereas caseins were detected during the initial 1-2 h effluents, and 3) immunoenzymo metric assay indicated that 64% and 44% of the beta-Ig and alpha-lac, respectively, were recovered in an intact antigenic form. Results indicate that the digestion of milk proteins in humans differs quantitatively. Digestion appeared partially incomplete in the upper jejunum, suggesting the importance of the ileum for completion of digestion.
Blotting, Western Caseins