Nature and Appearance of Protein Digestion Products in Upper Mesenteric Blood

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Abstract
Summary Dogs prepared with catheters in the superior mesenteric vein were fed meals of liver and homologous plasma protein. Analysis of the superior mesenteric blood plasma showed marked rises in amino acids up to 6 hours later. Digestion of the homologous plasma protein took essentially the same course as that of liver protein, contrary to results reported by others(7). No peptides were found and both proteins were apparently completely degraded to amino acids. Rises in lymph amino acids were qualitatively similar to those of the mesenteric plasma, though not as marked. An amino acid conjugate was isolated from all plasma samples, and its amino acid composition was determined. Its changing structure, and failure to respond in an obvious way to the meals leads us to believe that it is not of direct dietary origin.