Abstract: The purpose of this experiment was to study the effects of adding different doses of boron in drinking water on the microstructure, digestive enzyme activity, barrier function and antioxidant function of the rat ileum. One hundred freshly weaned clean-grade SD rats were randomly selected and divided into 10 groups (n =10) after one week of acclimatization. The control group was given distilled water, while the experimental groups I to IX were given distilled water containing 5, 10, 20, 40, 80, 160, 320, 480 and 640 mg/L of boron, respectively, for 60 days. The results showed that compared with the control group, the height of ileum villi and the number of goblet cells (GC) in rats given 5 mg/L of boron increased significantly (P < 0.01), the expression of the tight junction proteins ZO-1 (P < 0.05) and occludin (P < 0.01) increased significantly, and the activities of maltase (P < 0.05), lactase (P < 0.01), α-amylase (P < 0.01), lipase (P < 0.01), and superoxide dismutase (SOD) (P < 0.01), total antioxidant capacity (T-AOC) (P < 0.05) and the content of glutathione peroxidase (GSH-Px) (P < 0.01) also increased significantly. The numbers of ileal GC (P < 0.05) and intra-epithelial lymphocytes (IEL) (P < 0.01) increased significantly, the expression of secretory immunoglobulin A (SIg A) (P < 0.05), ZO-1 (P < 0.01) and occludin (P < 0.01) increased significantly, and the activities of lactase (P < 0.01), and SOD (P < 0.01) and GSH-Px content (P < 0.05) also increased significantly in the ileum of rats given 10 mg/L of boron in drinking water. In contrast, the number of GC (P < 0.01) and the number of IEL (P < 0.01) significantly decreased, SIg A (P < 0.01), ZO-1 (P < 0.05) and occludin (P < 0.01) expression significantly decreased, and the activity of maltase (P < 0.05) and T-AOC (P < 0.05) also significantly decreased in rats administered with 480 and 640 mg/L of boron in drinking water. These results suggest that drinking water supplementation with 5 and 10 mg/L of boron could improve the microstructure, enhance digestive enzyme activity, barrier function and antioxidant function of the rat ileum, whereas drinking water supplementation with 480 and 640 mg/L of boron could have the opposite effects.

Key words: boron; ileum; microstructure; digestive enzyme activity; barrier function; antioxidant function