Absorption of di- and tripeptides by the intestine of the guinea-pig.

: This paper describes a method of quantifying the amount of smaller peptides in physiological fluids and reports the preliminary results of studying the mesenteric blood of adult guinea-pigs during absorption of a partial hydrolysate of casein. Because of the different roles suggested for plasma and erythrocytes in the inter-organ transport of amino acids, both plasma and whole blood have been studied. Whole blood and plasma samples were deproteinized with sulphosalicylic acid, and amino acids and small peptides separated from residual small amounts of protein on a Sephadex G-25 column. Ion exchange chromatography was then performed before and after acid hydrolysis. The concentration of small peptides in blood seems to be much lower than was previously believed. The adult guinea-pig did not absorb small peptides across the intestine into mesenteric whole blood or plasma in our experiments. However, casein hydrolysates are not necessarily representative of all protein hydrolysates, and further studies are required using different proteins and varying degrees of hydrolysis. The possibility of peptide transfer during development, and in conditions involving mucosal damage, should also be investigated. The present investigation confirms the assumption that predominantly plasma, and not red blood corpuscles, carries amino acids from the gut to the liver. It is worth noting, however, that taurine, aspartic acid, glutamic acid, citrulline and arginine were found in higher concentrations in whole mesenteric blood than in plasma.