24. ORAL REHYDRATION THERAPY: A SOLUTION TO THE PROBLEM

Abstract

In previous studies, an oral rehydration solution containing glycine (gly) and a glucose polymer performed better than WHO–ORS in reversing water secretion in an animal model of secretory diarrhoea. We have now assessed the relative contribution of gly and glucose (glu) concentration and osmolality (osm) to the efficacy of oral rehydration solutions (ORS). After exposure to pure cholera toxin, whole rat small intestine was perfused in situ with 7 different ORS. All ORS derived from a basic solution (BORS) containing Na 50, K 25, Cl 75 and glu 50 mM, to which 25 or 50 mM of either gly, glu or mannitol was added. All ORS reversed water secretion to absorption with varying efficacy. Maximum water absorption was obtained with BORS (161±10 μl/min/g dry wt). When osm of BORS was raised to 225 and 250 mOsm/Kg by adding mannitol, water absorption decreased significantly (106±5 and 44±4 respectively, p<0.01). At each of these osm, substitution of mannitol by gly or glu resulted in similar increases in water absorption (p<0.02), but all modifications compared unfavourably with BORS. Na secretion occurred with all ORS tested, despite net water absorption. These results suggest that (1) osmolality is a key factor influencing the efficacy of ORS, (2) glycine has no advantage over glucose in promoting water absorption and (3) solutions with [glu]:[Na] ratio up to 2:1 are beneficial.