RELATIONSHIP BETWEEN GLUCOSE AND SODIUM IN ORAL REHYDRATION SOLUTIONS (ORS); STUDIES IN A MODEL OF SECRETORY DIARRHOEA

Abstract

Glucose sodium co-transport remains intact in enterotoxin - mediated diarrhoea, hence the rationale for rehydration with oral glucose electrolyte solutions. Using a technique of in situ perfusion in whole rat small intestine after exposure to cholera toxin (75μg for 2 hours) we evaluated the ability of seven different ORS (Glucose 111 or 202 m mol/l, sodium 35-90 m mol/l, osmolality 270-320 mOsm/kg, ratio of glucose: sodium concentration 1.2-5.8), to reverse net water secretion to absorption. Water absorption (+) in μl/min/g of dry wt intestine occurred with all ORS but was greater from ORS with a glucose: sodium ratio of 1.9 than from ORS with ratios of 1.2 and 5.8 ( + 98.6 ± 16 vs + 37.8 ± 8 vs 2.2 ± 7 respectively; p < 0.01). Hypotonic ORS (270 mOsm/kg were superior in promoting water absorption than ORS with osmalities of 312 and 330 mOsm/kg. Water absorption was less from the two ORS with glucose 202 m mol/l. (+ 2.2 ± 7 and 19.4 ± 4) than from the five ORS with glucose 111 m mol/l. (range + 37.8 ± 8 to + 101.9 ± 12; p < 0.01). ORS with 60 m mol/l of sodium were superior to those with 35 or 90 m mol/l. Efficacy of ORS in this model of secretory diarrhoea depends not only on glucose and sodium concentration but on the glucose: sodium ratio and osmolality. These studies may guide development of new, more effective ORS.