Primary and secondary transport systems for amino acids in the intact intestine.

Abstract

IN OUR PREVIOUS INVESTIGATIONS we have been able to demonstrate the net and absolute absorption rates for amino acids from the small intestine in the intact rat. 1 We also demonstrated that absorption could be inhibited by inducing pyridoxine deficiency and by the antimetabolites deoxypyridoxine and 2, 4-dinitrophenol (DNP). Alleviation of this inhibition was dependent upon the B6-vitamin factor in the form of pyridoxal-5-phosphate. 1,2 The problem with which we were confronted was to investigate whether or not this inhibition of mediated intestinal absorption was one in which the cells of the mucosa were affected so that they could not selectively take up the amino acid, or could accept a normal load but not pass this on to the circulation. These experiments are intended to show that the inhibited absorption is involved in what we might postulate as a secondary transport system from the loaded intestinal cells rather than