Absorption of neutral amino acids by the gut ofArenicola marina

Summary The absorption of neutral amino acids byArenicola marina was studied using anin vitro preparation of the alimentary canal. Regional variation in absorption was observed, with the intestine being the region of greatest uptake. The L enantiomorphs of the neutral amino acids alanine and leucine were shown to be actively absorbed by the intestine as was the D enantiomorph of alanine. A saturable component was demonstrated in the absorption of L-alanine and this was shared by L-methionine, which was found to competitively inhibit alanine uptake. Inhibition of L-alanine uptake also occurred in the presence of other neutral, basic and acidic amino acids. The greatest inhibition was found with the L stereoisomers of methionine, leucine, valine, histidine and phenylalanine, whilst proline, lysine and aspartic acid decreased uptake to a smaller extent.