DIGESTION PATTERNS OF ENDOGENOUS AND DIFFERENT EXOGENOUS PROTEINS AFFECT THE COMPOSITION OF INTESTINAL EFFLUENTS IN HUMANS

The purpose of this work was to determine if endogenous luminal protei ns are stimulated differently by various dietary proteins and if their digestibility differs from that of dietary proteins. Intestinal efflu ents were collected from the jejunum of four volunteers who had previo usly fasted or ingested either casein or soybean proteins. After separ ating the jejunal digested fraction (nonprotein nitrogen) by dialysis, the protein nitrogen fractions of the effluents and of the protein so urces were further hydrolyzed in vitro in a digestion cell with simult aneous dialysis of the digestion by-products. The results indicated a higher (P < 0.05) gastrojejunal absorption of casein (64.5 +/- 2.5%) c ompared with soybean protein (49.9 +/- 4.1%) in humans. Compared with fasting conditions, protein ingestion increased both the total nitroge n and protein nitrogen of the endogenous nitrogen fraction slightly (P < 0.05) but had no effect on the nonprotein nitrogen fraction. The am ino acid profiles of the nonprotein nitrogen in the effluents differed from those of both the protein sources and their mixtures with endoge nous secretions. This was attributed to the specific release of amino acids by pancreatic enzymes as measured in vitro. The hydrolysis patte rns of amino acids were determined by the structure of food proteins a nd their interaction with endogenous proteins. Soybean and endogenous nitrogen had equivalent digestibilities when measured in vitro.