Increased dopamine receptor binding in duodenal mucosa of duodenal ulcer patients

High-affinity and saturable membrane-bound dopamine binding sites have been characterized in rat and human gastrointestinal tissues. Although their role in experimental ulcerogenesis has been suggested, dopamine receptor activity in peptic ulcer disease has not been investigated. Radioligand binding studies were performed with mucosal tissue homogenates obtained from the antrum and duodenum of six male healthy volunteers and six male duodenal ulcer patients. The binding assay was performed in triplicate with a crude membrane fraction using [3H]dopamine as a ligand at a final concentration of 1 nM at 22 degrees C in the dark. Nonspecific binding (which usually comprised about 30% of total binding) was determined in the presence of a 100-fold excess of unlabeled dopamine. A significant (P less than 0.05) increase of [3H]dopamine binding was found in duodenal mucosa of duodenal ulcer patients. [3H]Dopamine binding in stomach (antrum) of normal and duodenal ulcer patients did not differ significantly. These findings provide preliminary evidence for a role of dopamine receptors in duodenal ulcer and suggest that biochemical abnormalities of gut dopamine function may be operative in the pathogenesis of peptic ulcer disease.