The protective role of melatonin on small intestine after thioacetamide intoxication in rats

The present study deals with the effect of melatonin (MT), a very potent and efficient endogenous free radical scavenger, against the toxic effect induced by thioacetamide (TAA) on structure of small intestine in rats. Melatonin acts as a primary nonenzymatic antioxidant and protects the tissue from oxidative damage. Thioacetamide, which was originally used as a fungicide, is proposed hepatotoxin commonly used to induce liver cirrhosis in rats and other species. However, very little attention has been dealt with the effects of TAA on the intestinal cells and there functions. It was therefore of interest to study the aging variation in the sequenced responses of injury caused by TAA and regeneration capacity of recovery after using melatonin. For this purpose male Wistar rats aging 1, 3 and 12 months were arranged in three main groups (15 rats for each group). Each main group then divided into: (1) control group, (2) intoxicated group (a singe high dose 300 mg/kg/body weight of TAA) and (3) treated group, administered the same dose of thioacetamide with melatonin (5 mg/kg/body weight) daily injected orally for four weeks. Histological investigation of TAA intoxication revealed a highest grade of pathological alterations manifested by changes of width and length of most villi in ileum of all intoxicated groups. The epithelial cells lining the top of the villi were denuded in ileum sections of newly weaned and young intoxicated animals, while they appeared degenerated with exposed lamina propria in ileum sections of adult group. There was also an increase in the number of goblet cells in most villi and in crypts of Lieberkuhn of intestinal cells. Mitotic figures were observed obviously in the crypts of onset ileum cells of intoxicated animals. Lymphocytic infiltration in lamina propria and submucosa were more obvious in the intestinal cells of young intoxicated groups. However, congestion and dilatation of blood vessels were more pronounced in ileum sections of adult intestinal groups. The combined treatment with TAA and MT inhibited intestinal tissue damage. The recovery towards normal is more noticeable in ileum sections in newly weaned rats, delayed in those of young and low in the adult rats. The results for the present work indicated that melatonin could prevent cell death and intestinal dysfunction after TAA intoxication.