L-arginine in low concentration improves rat intestinal water and sodium absorption from oral rehydration solutions

The nitric oxide (NO) precursor L-arginine has been shown to produce variable effects on intestinal absorptive function, including ion transport.

To determine whether there is an optimal concentration of L-arginine, promoting proabsorptive effects from oral rehydration solutions (ORS) with 90 or 60 mM sodium.

In vivo perfusion of rat jejunum with determination of net water absorption, unidirectional fluid exchanges, sodium and calcium transport, and glucose absorption.

L-Arginine (1 mM) added to the 90 mM sodium ORS increased intestinal absorption of both sodium and water. Higher concentrations of L-arginine (2 to 10 mM) lacked this stimulatory effect. At 20 mM, L-arginine decreased sodium absorption below baseline. With a 60 mM sodium ORS, 2 mM L-arginine had a maximal fluid and electrolyte proabsorptive effect. At 20 mM L-arginine, net water absorption was indistinguishable from that obtained in the absence of L-arginine, and lower than with 2 mM L-arginine. Sodium absorption remained raised above baseline in perfusions with 10 and 20 mM L-arginine. Morphologically, villi from perfusions with increased absorption showed a large expansion of intercellular and lamina propria intercellular spaces.

Low concentrations of L-arginine seem to stimulate water and electrolyte absorption by the small intestine. This effect is consistent with NO induced vasodilation, may be vaso-constrictive and thereby reverse fluid and electrolyte transport.