The role of histamine in control of gastric mucosal blood flow in dogs

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.