SUMMARY The effects of an intravenous infusion of nicotine at a dose of 2.5, 5.0, 7*5, or 100 ,g kg-'h-' on pentagastrin-stimulated gastric mucosal blood flow and acid secretion were investigated in eight healthy male non-smokers. Each dose was tested in two males. Gastric neutral red clearance served as a measure of mucosal blood flow. Nicotine reduced volume secretion, acid secretion, and neutral red clearance in a dose dependent manner. In five healthy male smokers smokinf of five cigarettes per two hours induced similar changes to the intravenous infusion of 5 ,ug kg7 h71 nicotine. As volume secretion was inhibited more than neutral red clearance, it is concluded that nicotine increases blood supply to the gastric mucosa relatively to the reduced gastric secretion. Nicotine is either not associated with the development of peptic ulcers, or it exerts its ulcerogenic action via other mechanisms than change of acid secretion and gastric mucosal blood flow.Gastric and duodenal ulcers occur more frequently in smokers than in non-smokers.' 2 Peptic ulcers heal less well in smokers than in non-smokers.3?6 Since the work of Virchow, decreased mucosal blood flow has been thought to be one of the factors responsible for the loss of mucosal integrity in the upper gastrointestinal tract.7 8 In the following study the effects of intravenous nicotine infusion on gastric mucosal blood flow and acid secretion were investigated.Methods

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