Absorption of different amino acids by an intestinal preparation from normal rats and from rats exposed to supralethal X-Irradiation

Absorption of different amino acids [lysine, α-amino isobutyrate (AIB), methionine, alanine, glycine] was studied in an intestinal in vivo preparation from normal and X-irradiated rats (1 and 3 days after 2000 R). Absorption of amino acids under loading and in presence of other amino acids was also followed. Lysine and AIB absorption follow a saturation kinetics with a maximal velocity of 35 and 85.6 μmoles/min and a K_t of 10 and 67 μmoles for lysine and AIB respectively. Interference in absorption exists not only between amino acids of the same class, but also by lysine on neutral amino acids. One day after irradiation, absorption is normal or even enhanced, although active transport appears impaired as indicated by the increase in K_t. Three days after exposure, absorption, particularly the active one, is severely depressed. This is indicated by the low Vm and high K_t, as well as by the fact that loading has little influence on absorption.