Leucine absorption after mechanical obstruction of the rat small intestine.

Leucine absorption across the mechanically obstructed rat intestine was studied by in vivo and in vitro techniques. It varied between the early (after 2 h) and late (after 18 h) phases of the obstruction. During the early phase there was a reduction in mucosal uptake and in net absorption of the amino acid. At 18 h the inhibition in mucosal uptake was more prominent both above and below the occlusion site but net absorption was only reduced below the obstruction and was relatively unaffected above it. Mannitol and nonmediated leucine absorption were also increased above the obstruction. The findings during the late phase suggest the presence of an increase in leucine permeability across the intestine above the occlusion site. The observed normal rate of net leucine absorption across this segment is thought to be due to enhancement in intestinal diffusion which could be masking the depression in mucosal uptake.