Alanine stimulation of water and sodium absorption in a model of secretory diarrhea.

We investigated the effectiveness of L-alanine (Ala) addition to oral hydration solutions (OHSs) during secretory conditions induced by ileal instillation of 10 mM theophylline in anesthetized rats using a perfusion procedure, and monitoring water and sodium transport. Ala was added to two hypotonic OHSs in which the sodium:glucose ratio was 2:1, and compared with the OHS recommended by the World Health Organization (WHO), which has a sodium:glucose ratio of 0.81:1. Theophylline had the expected secretory effect on water and sodium absorption in the WHO-recommended OHS, and on sodium transport in a formula containing 60 mM sodium and 30 mM glucose. However, an OHS with 90 mM sodium and 45 mM glucose canceled the secretory effect of theophylline and yielded a greater rate of net water absorption than the WHO formula. Addition to this solution of either 15 or 30 mM Ala enhanced water and sodium absorption of both control and theophylline-treated rats. In the hypotonic OHS with 60 mM sodium and 30 mM glucose, Ala had little effect on both sodium and water transport. Therefore, the data support the view that Ala added to solutions with 90 mM sodium, containing sufficient glucose to maintain a sodium:glucose ratio of not less than 2:1, is most effective at compensating fluid and sodium losses under secretory conditions. Ala presumably exerts its sodium-sparing effect because of its cotransport with sodium and the consequent water influx into the intestinal cells.