Evaluation of oral rehydration solution by whole-gut perfusion in rats: effect of osmolarity, sodium concentration and resistant starch

Background: Reduced osmolarity oral rehydration solution (ORS) improved small bowel absorption of fluid and electrolytes in segmental perfusion in experimental animals; this was borne out in clinical practice. Adding amylase-resistant starch (RS) to ORS is expected to increase colonic fluid absorption. This study used combined small and large bowel perfusion to evaluate combinations of reduced osmolarity and starch in ORS. Methods: Single-pass steady-state perfusions of the whole gut at 30 mL/h, using the nonabsorbable marker 14C-polyethylene glycol 4000, were performed in Wistar rats after exposure to cholera toxin or Escherichia coli heat-stable enterotoxin (STa). Results: Steady state was established within 90 minutes after commencing perfusion. Net secretion of water, sodium and chloride induced by cholera toxin was partially reversed by standard glucose-ORS (G-ORS). Substituting glucose in G-ORS with RS (RS-ORS) substantially increased net water absorption (P < 0.001) as did reduced osmolarity ORS (RO-ORS) (P < 0.001); addition of RS to RO-ORS further increased water absorption (P < 0.001). In STa-treated intestine, RO-ORS and RS-ORS significantly improved water absorption compared to G-ORS (P < 0.005). RO- and RS-RO-ORS did not significantly augment net electrolyte absorption compared with G-ORS. RS-ORS was associated with highest net absorption of sodium and chloride compared with all other groups. Conclusions: RS increased net water (and sodium) absorption from isosmolar and reduced osmolar ORS consistent with increased absorption by the colon. RS in reduced osmolar ORS may have advantages to reduce severity of diarrhea and prevent hyponatremia in severe diarrhea and may be applicable to diarrhea of different etiologies