Modulation of jejunal flow by solutions of varying osmolality and acidity in the intact canine jejunum.

Because gastric emptying is modulated by the osmolality or hydrogen ion concentration of intraduodenal solutions, we hypothesized that similar mechanisms exist to regulate flow within the small intestine and that the altered flow is associated with changes in intestinal motility. Sodium chloride solutions with higher and lower osmolality than plasma and both isotonic and hypotonic hydrochloric acid solutions flowed more slowly into segments of jejunum in conscious dogs than isotonic neutral salt solutions. The altered flow was associated with increased frequency of spike bursts in the segment with the salt solutions of varied osmolality, but with only increased force of contractions with both isotonic and hypotonic acid solutions. Some evidence exists to suggest that the changes in motility are mediated by a neural mechanism. If similar mechanisms exist in the duodenum, they may play a role in the regulation of gastric emptying.