Effects of histamine H-1 antagonist dithiaden on acetic acid-induced colitis in rats

To assess the possible involvement of mast cells and/or their mediators in inflammatory bowel diseases, the effect of the histamine H-1 antagonist Dit hiaden was studied on a model of acetic acid-induced colitis in rats. Dithi aden pretreatment by intracolonic administration was found to reduce the ex tent of acute inflammatory colonic injury. This was manifested by a decreas e in the score of gross mucosal injury, by lowered colonic wet weight and b y diminished myeloperoxidase activity reflecting reduced leukocyte infiltra tion. Vascular permeability and gamma-glutamyl transpeptidase activity, ele vated by acetic acid exposure, were decreased after Dithiaden pretreatment. The results indicate that locally administered Dithiaden may protect the c olonic mucosa against an acute inflammatory attack by interfering with the action of the major mast cell mediator histamine.