Is administration of n-3 fatty acids by mucosal enema protective against trinitrobenzene-induced colitis in rats?

We investigated the protective role of fish oil (FO-source of n-3 FA) enric hed diet tin the first protocol in 20 rats and FO administration intrarecta lly (in the second protocol) in 40 rats with trinitrobennzene (TNB) colitis . All colonic specimens were pathologically evaluated, myeloperoxidase enzy me activities were measured, leukotriene B4 (LTB4) and LTC4 levels were det ermined by radioimmunoassay. In the first protocol 10 rats (group Al) were fed with 8% sunflower and cotton oil enriched diet and (group A2) with 8% F O enriched diet for 6 weeks. At the end of this period, TNB (30 mg in 0.25 mi of 30% ethanol) were intrarectally administered. After 2 weeks, rats wer e sacrificed. MPO activities (2.47 versus 30.17), LTB4 (34.5 versus 903.3) and LTC4 (77.7 versus 456.0) levels were significantly reduced in group A2 compared with group Al (P < 0.005). There was also a significant difference in pathologic scores (1.55 versus 2.12, P < 0.0002) between two groups. In the first part of the second protocol, 20 male rats were randomized into t wo equal groups (B1 and B2) and TNB colitis was induced. After 1 day, 1 mi of saline (group B1) or n-3 FA enemas (group B2) were administered every da y for 2 weeks. At the end of this period, rats were sacrificed and evaluate d as done for previous groups. Although there was no significant difference between the two groups in comparison with MPO enzyme activities and pathol ogic scores, the LTB4 (130.1 versus 971.0) and LTC4 (126.0 versus 532.0) le vels of FO group were significantly reduced (P < 0.005). In the second part of the second protocol, 20 male rats were randomized into two groups. One millilitre of saline (group B3) or FO enemas (group B4) were administered t o rats every day for 3 days. At the fourth day, TNB-colitis was induced and after 24 h rats were sacrificed. We could not find any significant differe nce in MPO activities, pathologic scores, LTB4 and LTC4 levels between grou ps B3 and B4. In conclusion; FO enriched diet decreased both pathologic dam age and tissue LT levels. The second protocol of our study revealed that th e long-term FO enemas decreased the LTB4 and LTC4 levels; however, did not have any beneficial effect on the tissue lesions. Short periods of FO enema s did not have a protective role in the occurrence of experimental colitis. The present study showed that FO enemas significantly decreased LT levels. The protective effect of FO (oral and enema) in TNB colitis may open a new insight into the treatment of inflammatory bowel disease. (C) 1999 Harcour t Publishers Ltd.