Glycolysis as an energy source for intestinal transport of amino acids: Comparison between rat and guinea-pig

1. 1. Active transport of phenylalanine by rat intestinal rings is almost completely abolished by anaerobiosis or by 2:4-dinitrophenol. When glucose is added to the incubation medium, this inhibition is partially reversed. This effect of glucose is not observed with guinea-pig intestine. 2. 2. Phenylalanine transport is inhibited by n-butyl-biguanide in both species, but whereas glucose stimulates transport in the presence of biguanide in the rat intestine, it provokes a greater inhibition in that of the guinea-pig. 3. 3. In rat intestine, non-metabolizable but actively transported sugars such as galactose also cause further inhibition. 4. 4. In both species, glucose alone, like other transportable sugars, inhibits phenylalanine uptake. Glucose does not influence the inhibition provoked in the rat intestine by ethacrynic acid, an inhibitor of glycolysis as well as transport. 5. 5. These results reveal the interplay between two effects of glucose on phenylalanine transport in the rat intestine, namely the interaction between sugar and amino acid transports at the level of the luminal membrane, and the production of energy by intracellular glycolysis. Since the latter process is much less marked in the guinea-pig mucosa, the former interaction is preponderant in that species.