Abstract
The role of the histamine receptors in the control of gastric mucosal blood flow was evaluated in dogs utilizing [ 14C]aminopyrine ([ 14C]AP) clearance techniques. Because of the importance of maintaining a low intragastric pH to prevent dissociation of AP and back diffusion through the gastric mucosa, AP was traped in the stomach lumen by intragastric perfusion of a marker solution with a pH of 1.16. Results obtained utilizing a marker to determine gastric secretory volume and gastric juice [ 14C]AP concentration correlated well with those values obtained from direct measurements from fluid collected from a gastric fistula. Histamine base administration increased [ 14C]AP clearance. Cimetidine, an H 2 receptor antagonist, did not significantly change basal [ 14C]AP clearance and inhibited [ 14C]AP clearance at low doses of histamine administration. An H 2 receptor agonist (4-methylhistamine) and an H 1 receptor agonist (2-methylhistamine) each increased mucosal blood flow approximately 30% and 70%, respectively, of the response produced by histamine base. Blood flow stimulated by 2-methylhistamine was inhibited by the H 1 receptor antagonist diphenhydramine. The results suggest that histamine H 1 and H 2 receptors are involved in the control of canine gastric mucosal blood flow.
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