ビールに含まれるN-メチルチラミンの膵外分泌刺激効果

抄録

Alcoholic beverages contain several congeners. N-methyltyramine (NMT) was isolated from beer as a factor to stimulate gastric acid secretion. We examined whether NMT stimulated pancreatic secretion in conscious rats. Methods: Male Wistar rats (330g) were prepared with cannulae for draining bile and pancreatic juice separately, with two duodenal cannulae, with a gastric cannula, and with an external jugular vein cannula. The rats were placed in modified Bollman-type restraint cages. After the 4-day recovery period, the experiments were conducted in unanesthetized rats. Different concentrations of NMT solutions (5, 25, and 50 micro-g/kg/3ml/3min) were infused into the stomach. NMT content in beer was 2mg/L, so that if 50kg body weight man consumes a bottle of beer, 25 micro-g/kg NMT will be ingested. To examine the mechanism, the effects of proton pump inhibitor, CCK-BR antagonist, CCK-AR antagonist and atropine were administered prior to the NMT infusion. The effect of intravenous infusion of NMT (2.5 micro-g/rat) was also determined. Results: Intragastric administration of NMT significantly increased pancreatic exocrine secretion in a dose dependent manner. Atropine abolished the stimulatory effect of NMT, but others did not. Intravenous infusion of NMT did not affect pancreatic secretion. Conclusions: NMT stimulates pancreatic secretion via cholinergic gastro-pancreatic reflex. Therefore, the stimulatory effect of beer on pancreatic secretion was produced by not only ethanol but also a congener, NMT. [J Physiol Sci. 2006;56 Suppl:S78]