Response of the small intestine to the application of a hypertonic solution

The morphologic and functional alterations caused by a commonly used hypertonic radiographic dye (Hypaque(R)-50%) were compared with changes observed during the absorption of 150 mM saline in closed segments of the ileum of 2- to 3-kg rabbits. Hypertonic dye caused a rapid decrease in height and width of the villi, a decrease in height of the epithelial cells and closure of the intercellular space. Concomitantly, the tissue fluid content of the bowel wall and the volume of venous outflow from the segment of ileum decreased, presumably in response to the osmotic gradient between ileal lumen and blood. The fluid added to the luminal contents was hypotonic and contained sodium, potassium, chloride and bicarbonate. In contrast, the ileum exposed to 150 mM saline had prominent intercellular spaces between adjacent epithelial cells and absorbed the solution at isotonic conditions. These studies indicate that production of diarrheal fluid by this hypertonic solution is different from that reported for enteric pathogens.