Objective: Although chemicals including trinitrobenzenesulfonic acid (TNBS) and dextran sodium sulfate (DSS) are widely used to induce ulcerative colitis (UC) in laboratory animals, they are expensive and have side effects. This study aimed to introduce a novel model of chronic UC using ammonium chloride as an inexpensive material.

Materials and Methods: In this in-vivo study, 21 adult male Sprague Dawley rats were divided into three equal groups as follows: the first group (control) was received 0.5 cc of distilled water and the second and third groups were received 0.5 cc of ammonium chloride at concentrations of 2 mol/L or 4 mol/L through rectal enemas for 14 consecutive days (once daily). The procedure was stopped for two weeks, and then started and continued till rectal bleeding was observed. At the end, animals were sacrificed and colon, liver, and kidney tissues were examined histopathologically.

Results: Although gross observation of colons in the control group showed a normal structure without histopathological changes, rectal enemas with 2 mol/L ammonium chloride caused hemorrhagic areas as well as mild edema of the sub mucosal layer and inflammatory cell infiltration. Besides, rectal enemas with 4 mol/L ammonium chloride caused an extensive ulceration/necrosis, severe inflammation and edema, moderate fibrinous exudate, and mild atrophy of intestinal glands. The liver and kidney tissues were normal in all groups.

Conclusion: Based on the findings, ammonium chloride can be used as an inexpensive alternative for inducing a chronic model of UC in rat. Current model also fulfills the histopathological criteria of UC.