RESUMEN
Plasma levels of nitric oxide [NO] and alpha-tocopherol as well as catalase activities in colon and liver tissues were assessed in 1, 2 dimethylhydrazine-induced colon cancer rats. Five groups of male Sprague-Dawley rats were fed the experimental diets supplemented with Allium sativum powder and Nigella sativa seeds [2.5%, 5%] or a mixed dose of both plants [5% of each] for 24 weeks, experimental period. At the fifth week rats were subcutaneously injected with dimethylhydrazine dihydrochloride [DMH] at a dose of 20mg/kg body weight for 20 weeks. Another two groups of rats were fed the basal diet for the same period, the first group designed as negative control group and injected with saline solution while the second group was injected with DMH at the same dose and designed as positive control group. Colon carcinogenesis was accompanied by a significant increase in the level of NO as well as catalase activity and significant decrease in plasma levels of alpha-tocopherol. Only the 5% Allium sativum powder fed group exhibited a significant decrease in NO level. Administration of Allium sativum powder and the mixed dose caused significant decrease in colonic and hepatic catalase activities and significant increase in alpha-tocopherol levels. On the other hand, the effects of Nigella sativa seeds on the measured parameters were non significant. These results were confirmed by the histopathological results that showed low incidence of colon tumors in rats fed 5% Allium sativum powder [17%] and the mixed dose [56%] fed groups. It could be concluded that the promising effect of garlic in DMH-induced colon cancer rats may be mediated through modulation of plasma levels of nitric oxide and alpha-tocopherol as well as tissue catalase activity