Effect of Boron on Microstructure, Immune Function, Expression of Tight Junction Protein, Cell Proliferation and Apoptosis of Duodenum in Rats.

Boron is an essential trace element for animals. Appropriate boron supplementation can produce beneficial effects on the animal body, while a high dose of boron has adverse and even toxic effects. Our aim was to investigate the impact of different doses of boron on the microstructure of duodenum in rats, expression of secretory immunoglobulin A (SIgA) and tight junction protein, cell proliferation and apoptosis. Eighty newly weaned clean Sprague-Dawley (SD) rats were given distilled water supplemented with 0, 10, 20, 40, 80, 160, 320, and 640 mg/L of boron for 60 days. We found that supplementation of 40 and 80 mg/L boron could increase the height of duodenal villi and the crypt depth, the number of intraepithelial lymphocytes (IELs) and goblet cells, the expression of SIgA, Zonula occludens-1 (ZO-1) and occludin, and proliferating cell nuclear antigen (PCNA) in duodenum of rats; decrease expression of Caspase-3 mRNA and the number of Caspase-3-positive cells, but supplementation of 320 and 640 mg/L boron could have the opposite effect in these indexes. The results showed that supplemented with 40 and 80 mg/L of boron could improve the structure and function of duodenum, while supplemented with 320-640 mg/L had a significant inhibitory effect.