IT HAS BEEN DEMONSTRATED that amino acids are absorbed from the small intestine by an "active" as well as passive process. It is also apparent that vitamin B6 plays a role in the active process of cellular uptake of amino acids, and that the antimetabolites deoxypyridoxine and 2,4-dinitrophenol (DNP) have an inhibitory effect upon active absorptive processes.
The problem was to show that amino acid absorption in the upper small intestine of the living intact rat is an active process dependent upon at least one of the B6-vitamin factors. Experimental evidence shows that of the B6 vitamins, pyridoxal-5-phosphate plays a role in an active (mediated) process in the intact animal.
Intestinal absorption of L-methionine and L-tyrosine was investigated by use of a perfusion technique, in situ, which allows for study of the continuous rates and net or absolute loads, or both, absorbed from perfused upper small intestinal segments in
Jacobs FA. Role of Vitamin B6 in Intestinal Absorption of Amino Acids in Situ. JAMA. 1962;179(7):523-525. doi:10.1001/jama.1962.03050070000009