Editor,—Wapnir et al (Gut1997;40:602–7) reported interesting observations on the effect of l-arginine in low concentrations on intestinal water and sodium absorption from rat jejunum, in experiments which they carried out to determine the possible proabsorptive effect of this amino acid if included in oral rehydration solutions. Their results, showing that perfusion of very low concentrations of arginine stimulated sodium and water absorption, but higher concentrations had the reverse effect, recalled to mind observations we made many years ago in the course of a systematic study of the effect of amino acids on sodium and water absorption in human jejunum.1

In double lumen intestinal …