A NOVEL NONNEURONAL CATECHOLAMINERGIC SYSTEM - EXOCRINE PANCREAS SYNTHESIZES AND RELEASES DOPAMINE

Cells of the exocrine pancreas produce digestive enzymes potentially h armful to the intestinal mucosa. Dopamine has been reported to protect against mucosal injury, In looking for the source of dopamine in the small intestine, we found that the duodenal juice contains high levels of dopamine and that the pancreas itself has a high dopamine [and dih ydroxyphenylalanine (dopa)] content that does not change significantly after chemical sympathectomy. Furthermore, we were able to demonstrat e tyrosine hydroxylase (TH) activity in control pancreas as well as in pancreas from rats after chemical sympathectomy. Immunostaining and i n situ hybridization histochemistry confirmed both the presence of TH, dopamine, and the dopamine transporter, and the mRNAs encoding TH and dopamine transporter, and the presence of both types of vesicular mon oamine transporters in the exocrine cells of the pancreas. Since there are no catecholaminergic enteric ganglia in the pancreas, the above r esults indicate that pancreatic cells have all the characteristics of dopamine-producing cells. We suggest that the pancreas is an important source of nonneuronal dopamine in the body, and that this dopamine ha s a role in protecting the intestinal mucosa and suggests that dopamin e D1b receptor agonists might be used to help mucosal healing in the g astrointestinal tract.