Selective absorption of stereo-isomers of amino-acids from loops of the small intestine of the rat

Abstract

Amino-acids may be absorbed from the small in- testine in two ways, either by diffusion alone, or by a method involving an active process in one or more steps. Previous work has supported both possi- bilities. Hober & Hober (1937) found that the rate of entry of glycine, alanine and valine was not pro- portional to the concentration in the gut. They also found that these amino-acids were absorbed faster than polyhydric alcohols of comparable molecular volume and concluded that an active process was involved. On the other hand, Kratzer (1944) re- ported that the rate of disappearance of amino-acids from the gut was inversely proportional to their molecular volume, while Chase & Lewis (1934), com- paring the rates of disappearance of several L-and DL-amino-acids, found no difference between the L- isomers and the racemic mixtures. Simple diffusion would account for these results.