L‐arginine in low concentration does not enhance intestinal water absorption from a dilute glucose‐electrolyte solution in healthy humans

Background: In humans, addition of 5 – 40 mM L‐arginine (LA) to an isotonic saline solution causes net water secretion in the jejunum (Hegarty et al., Gut 22 :–113, 1981). However, in rats, 2 – 10 mM LA enhances water absorption of an oral rehydration solution (Wapnir et al.; Gut 40 :–607, 1997). The purpose of this study was to determine if low concentrations of LA enhance water absorption from a dilute glucose‐electrolyte solution in healthy humans. Methods: Six subjects participated (mean ± SD age = 23 ± 2 yr). Four solutions were tested and net water flux was determined by segmental perfusion in the duodenojejunum. Solutions were: 222 mM glucose (G), 222 mM glucose + 1.5 mM LA (G + 1.5 LA), 222 mM glucose + 3 mM LA (G + 3 LA), and 222 mm fructose + 1.5 mM LA (F + 1.5 LA). Solutions also contained 20 mEq sodium, 3 mEq potassium, and had osmolalities of ~270 mOsm. Results: Water absorption was not different among G, G + 1.5 LA, and G + 3 LA (means ± SD = 3.7 ± 1.1, 4.0 ± 1.6, and 4.5 ± 2.0 ml/h/cm, respectively). Each of those promoted faster (P < 0.05) absorption than F + 1.5 LA (0.5 ± 1.2 ml/h/cm). Conclusions: LA (1.5 – 3 mM) did not enhance water absorption rate from a dilute glucose‐electrolyte solution, however, glucose promoted a faster rate than fructose. Addition of LA does not appear beneficial for water absorption of fluid replacement solutions in healthy humans. Supported by the Gatorade Sports Science Institute