Changes in the inflammatory mediator content in the colonic mucosae of immune colitides in guinea pigs (Abstract)

Abstract

An immune colitis based on a delayed-type hypersensitivity reaction was induced in dinitrochlorobenzene (DNCB) sensitized guinea pigs by intrarectal challenge with DNCB in Orabase (Squibb Ltd.)¹. A low challenge dose (0.25% DNCB), given once daily for 5 days induced mild inflammatory changes in the distal colon and rectum characterized by goblet cell depletion and mild cellular infiltration of the mucosa and submucosa. A higher challenge concentration (5% DNCB) given once daily for 3 days resulted in severe colonic ulceration with crypt abscess formation and a heavy cellular infiltrate in the mucosa and sub-mucosa. Diarrhoea, rectal bleeding and body weight loss were also prominent features. The inflammatory mediators, histamine, 5-HT, glandular kallikrein and PGE₂ were measured in freeze-dried colonic mucosae of the two colitides. Histamine content was 3 times control (p< 0.01) in 0.25% DNCB induced colitis, although no significant change was observed in 5% DNCB challenged animals. Mucosal 5-HT content was significantly reduced (p < 0.01) in both models. Glandular kallikrein content did not differ from control (p > 0.05) PGE₂ was significantly increased (p < 0.05) in both models. The possible significance of these changes with respect to severity of inflammation and aetiology of colitis is described.