EVIDENCE OF A DOMINANT ROLE FOR LOW-OSMOLALITY IN THE EFFICACY OF CEREAL-BASED ORAL REHYDRATION SOLUTIONS - STUDIES IN A MODEL OF SECRETORYDIARRHEA

Clinical trials suggest that including naturally occurring complex car bohydrate in oral rehydration solutions (ORS) in place of glucose incr eases water absorption and reduces stool volume during acute diarrhoea . The mechanisms for this greater clinical efficacy has not been estab lished. This study examined the ability of two hypotonic rice based OR S, RS-ORS (137 mOsm/kg) and RP-ORS (143 mOsm/kg), and HYPO-ORS (240 mO sm/kg) a glucose equivalent ORS, to effect water absorption by in vivo perfusion of normal and secreting rat small intestine. The results we re compared with those for two widely used conventional hypertonic ORS , WHO-ORS (331 mOsm/kg) and UK-ORS (310 mOsm/kg). In the normal intest ine, water absorption was similar from WHO-ORS (87.4 (45.1-124.6) mul/ min/g; median and interquartile range) and UK-ORS (57.6 (41.5-87)) but less than from the hypotonic solutions (p<0.02); water absorption fro m RS-ORS (181.8 (168.5-193.8)) and RP-ORS (195.7 (179.3-207.9)) was si milar but less than from HYPO-ORS (241.3 (230.6-279.7); p<0.005). In t he secreting intestine, all ORS reversed net secretion of fluid to net absorption; the hypotonic solutions, HYPO-ORS (105.2 (95.2-111)), RS- ORS (127.7 (118.3-169.4)) and RP-ORS (133.7 (122.1-174.5)), produced m ore water absorption (p<0.005) than the hypertonic solutions WHO-ORS ( 47.1 (29-75.9)) and UK-ORS (24.9 (18.4-29.4)). The rice based solution s promoted most water absorption in secreting intestine (p<0.007). The se data indicate that low osmolality is of primary importance in media ting the increased water absorption from cereal based ORS.